Climate Notes
(last updated: Dec 27, 2007)

This page contains rough notes and/or detailed information about various climate issues, intended to supplement the web page on the Science of Climate Change.

New...

The surface area of the Earth is 510,072,000 km², or 5.1 x 108 x 106 = 5.1 x 1014
Carbon added by humans to the atmosphere: 100 ppm x 2.1 Gt / ppm x 1012 kg / Gt = 2.1 x 1014 kg.
Therefore 2.1 x 1014 kg / 5.1 x 1014 m² , or 0.4 kg per square meter.

Atmospheric Pressure is 1 kilogram per square centimeter of surface area, or 10,000 kg / m². [ref]
Carbon dioxide has increased by 0.01% of the atmosphere (by volume).
Therefore 0.01% x 10,000 kg / m² = 1 kg / m², but only 1/3 of that is carbon, so we get 0.33 kg / m².

In a study that analyzed temperatures around the globe, researchers found that Earth has been warming rapidly, nearly 0.36 degrees Fahrenheit (0.2 degrees Celsius) in the last 30 years...  in a 2003 study, scientists showed that 1,700 plant and animal species migrated toward the poles at about 4 miles per decade in the last 50 years. That migration rate is not fast enough to keep up with the current rate of movement of a given temperature zone, which has reached about 25 miles (40 kilometers) per decade in the period 1975 to 2005, Hanson and co-authors write in the current issue of the journal Proceedings of the National Academy of Sciences  (ref)

In a warm climate, the Hadley cell gets weaker, the cell gets wider, and the jets and storm tracks penetrate further poleward. This all goes under the general rubric of "expansion of the tropics," [rc]

Nordhaus Economic Model

If you drive 10,000 miles a year in a car that gets 28 miles per gallon. Your car will emit about 1 ton of carbon per year.

CO2, which has a weight of 3.67 times the weight of carbon.

A typical U.S. household, which uses about 10,000 kilowatt-hour (kWh) of electricity each year. If this electricity is generated from coal, this would release about 3 tons of carbon.

For example, if a country wished to impose a carbon tax of \$30 per ton of carbon, this would involve a tax on gasoline of about 9 cents per gallon. Similarly, the tax on electricity would be
about 1 cent per kWh, or 10 percent of the current retail price, on coal-generated electricity.
 \$100 per ton carbon \$100 per ton CO2 Added Cost of Gasoline \$2.50 per liter 68 cents per liter Added Cost of Electricity 3.3 cents per kilowatt hour 0.9 cents per kilowatt hour

 Annual Emissions CO2 Concentration Temperature Reference 450 ppm SPM 1000 ppm SPM 19 Gt 685 ppm 5.3

Slide show: 200 million years of Antarctica's drift

Modelling Climate and Climate Sensitivity

The equation below illustrates the major factors governing the temperature of the Earth.  The left side describes the incoming solar energy and how some is lost to the reflectivity (albedo) of the planet.  The right side is about energy radiated back into space.  T is the temperature at which the Earth radiates energy, which decreases as greenhouse gas levels rise.

 Earth's Energy Balance Equation (S / 4)  (1 - albedo)  =  σ  ε  T4 S = albedo = σ = ε = T = Solar Energy received from the Sun. Reflectivity of the Earth's surface the Stefan Boltzmann constant A measure of how efficiently the Earth dissipates heat Temperature of the earth-atmosphere system, in °K

The new best estimate based on the published results for the radiative forcing due to a doubling of CO2 is 3.7 Wm-2, which is a reduction of 15% compared to the SAR. The forcing since pre-industrial times in the SAR was estimated to be 1.56 Wm-2; this is now altered to 1.46 Wm-2. [IPCC 6.3.1]

The radiative forcing due to CH4 is 0.48 Wm-2 since pre-industrial times (and 0.15 for N2O). [IPCC 6.3.2]

The radiative forcing due to all well-mixed greenhouse gases since pre-industrial times was estimated to be 2.45 Wm-2 in the SAR with an uncertainty of 15%. This is now altered to a radiative forcing of 2.43 Wm-2 with an uncertainty of 10%.

Radiative Forcing of Greenhouse Gases, from [IPCC Table 6.2]
 Greenhouse Gas Simplified Relative Forcing More complex version CO2 F = 5.35 ln(C/C0) F= 4.841 ln(C/C0) + 0.0906 (C - C0) CH4 F = 0.036 (M – M0) – (f(M,N0) – f(M0,N0)) N2O F= 0.12 (N – N0) – (f(M0,N) – f(M0,N0))
f(M,N) = 0.47 ln[1+2.01x10-5 (MN)0.75+5.31x10-15 M(MN)1.52]
C is  CO2 in ppm
M is CH4 in ppb
N is N2O in ppb

The calculated global mean radiative forcing of sulfate aerosol ranges from -0.26 to -0.82 Wm-2, although most lie in the range -0.26 to -0.4 Wm-2. Until differences in estimates of radiative forcing due to sulphate aerosol can be reconciled, a radiative forcing of -0.4 Wm-2 with a range of -0.2 to -0.8 Wm-2 is retained. [IPCC 6.7.2]

The estimate of the global mean radiative forcing for Black Carbon aerosols from fossil fuels is revised to +0.2 Wm-2 (from +0.1 Wm-2) with a range +0.1 to +0.4 Wm-2. [IPCC 6.7.3]

The estimate of the radiative forcing due to biomass burning aerosols remains at -0.2 Wm-2. The uncertainty associated with the radiative forcing is very difficult to estimate due to the limited number of studies available and is estimated as at least a factor of three, leading to a range of –0.07 to –0.6 Wm-2. [IPCC 6.7.5]

Therefore a tentative range of -0.6 to +0.4 Wm-2 is adopted for mineral dust; a best estimate cannot be assigned as yet.

`E is change in forcingusing the derivative of Stefan-Boltzmann:dT/dE = 1/(4[sigma] T^3)dT/dF=1/(4σT3).gets:dT=[alpha]ln([CO2]/[CO2}orig)/(4[sigma] T^3)This is the equation without all feedbacks.Substituting a doubling CO2 level (unrealistic, according to Lomborg)and substituting T= 15 degreesC = 288.16KdT=5.35ln2/(4*5.6705E-08*(288.16^3))ordT=0.6833 centigrade for a doubling of CO2 !!That's physics. All the rest is models and hype.[ref]`

Converting Carbon Dioxide Increase into Temperature Change

The direct increase in radiative forcing (dE) caused by an increase in carbon dioxide levels, in watts per square meter, can be found by the equation

dE = 5.35 ln (C/Co)  W/m2

where C is the new carbon dioxide level (in parts per million, or ppm) and Co is the starting carbon dioxide level.   For example, CO2 concentration has risen from 270 to 370 ppm, so the equation gives 5.35 x ln(370/270) = 1.7 W/m2 raw forcing.

According to the Stefan-Boltzmann equation: Power per unit area (W/m2)  = σ  ε  T4
σ = the Stefan Boltzmann constant, or 5.6703 x 10-8 Watts / m2 °K
ε = A measure of how efficiently the Earth dissipates heat, here assumed to be 1.
T = Temperature of the earth-atmosphere system, in °K

Taking the derivative, we get

dT / dE = 1 / ( 4 σ T3 )
Thus
dT =  5.35 ln (C/Co) / ( 4 σ T3 )

T should be the radiating temperature of the planet, since the greenhouse effect work because the Earth radiates at a colder temperature than the surface. The radiating temperature is about 255K.  [But what is the relationship between the Earth's radiating temperature and the suface temperature?]

 Initial CO2 (ppm) Final CO2 (ppm) Top of atmosphere (°K) Climate Sensitivity 5.35 ln (C/Co) = Watts per square meter direct forcing. 5.35 ln (C/Co) / ( 4 σ T3 ) =  °C direct warming;    Adjusted =  °C Total warming using climate sensitivity =   °C

the proof that global warming is anthropogenic is that night and winter temperatures are rising faster than when the sun is shining. If the warming was natural then it must be due to the sun. Therefore, day and summer temperature would show the greatest increase.)

The net amount of solar radiation arriving on a 1 m 2 area (perpendicular to sun) on the earth's surface is S(1- albedo).

From the point of view of the sun, the earth appears to be a disk with a radius R, so the total amount of power absorbed by the whole earth is the product of the arriving solar radiation times the area of a disk the size of the earth: PGain = π R2 S(1-alpha)

Any object at a temperature TK (in Kelvin) will emit thermal radiation at a rate given by: PLoss= epsilon σTK4 times it surface area. The factor epsilon is the emissivity (approximately 1), sigma is Stefan's constant, and the total surface area of the spherical earth (4 π R2). Recall that a temperature in Kelvin is TK=T0+T where T is the temperature in centigrade and T0=273.15

π R2 S(1-albedo) = (4 π R2) σ(T+T0)4

where T is the average temperature of the earth in centigrade. Solving for T gives the following equation:

T = [S(1-albedo)/4 / σ] 1/4-T0.

Where the symbols are defined as:
 T The Temperature of the Earth in Centigrade S Solar Constant (1370 W/m2) albedo Albedo - Fraction of incident solar radiation reflected (about 0.32) σ Stefan's Constant (5.6696E-8 W/m2K4) T0 Conversion from Kelvin to Centigrade (273.15)

[ref]

The radiative forcing for CO2 is roughly proportional to the logarithm  4.4log(C) / log(2)  of its concentration, while for CH4, the forcing scales like the square root [IPCC, 2001]. This implies that the higher the base level, the smaller the forcing will be from a fixed increase in concentration. [ref: [26]]  Using CO2 concentrations of 270 and 540 ppm of , we get 35.5 W/m2 and 39.0 W/m2, a difference of 4.4 W/m2.

From this NOAA web page:  (also this overview)

...net planetary radiative forcing changes roughly linearly in response to logarithmic changes in CO2. Thus, a quadrupling of CO2 gives another roughly 1°C direct warming over the direct 1°C warming for a CO2 doubling, valid for the extreme assumption that water vapor mixing ratios and clouds do not change.

The log-linear relationship has been found to hold down to CO2 concentrations to as low as one sixty-fourth of preindustrial levels. As CO2 is decreased, the atmosphere's ability to hold water vapor collapses and the global temperatures drop sharply.  [ref]

A Quick Calculation of Climate Sensitivity for the 20th Century

We can use the climate forcing figures from the above table, plus the fact that global average temperature increased by 0.8 ºC, to calculate the temperature rise for the equivalent of a doubling of carbon dioxide. The net forcing for the 20th century is 1.6 W/m2. From this we must subtract the estimated 0.3 W/m2 of energy that has been absorbed by the ocean, thus not included in the surface temperature (from Lyman et. al.)  The forcing from a full doubling of CO2 is 3.7 W/m2, therefore the observed temperature increase is found my multiplying the temperature increase by the ratio of the present forcing to a full CO2 doubling:

0.8 ºC * 3.7 W/m2  /  ( 1.6 W/m2 - 0.3 W/m2 ) = 2.3 C

This is a bit less than the standard 3 ºC estimate for a CO2 doubling. But the uncertainty in these figures is large, so this value fits well within the range of the IPCC estimates.

From Hansen 2008:

Climate forcing in the LGM equilibrium state, relative to the Holocene, due to the slowfeedback ice age surface properties, i.e., increased ice area, different vegetation distribution, and continental shelf exposure, was -3.5 ± 1 W/m2 (10). The forcing due to reduced amounts of longlived
GHGs (CO2, CH4, N2O) was -3 ± 0.5 W/m2, with the indirect effects of CH4 on tropospheric ozone and stratospheric water vapor included (fig. S1). The combined 6.5 W/m2 forcing and global surface temperature change of 5 ± 1°C relative to the Holocene (10b,c), yields an empirical sensitivity ~¾ ± ¼ °C per W/m2 forcing, i.e., a Charney sensitivity of 3 ± 1 °C for the 4 W/m2 forcing of doubled CO2. This empirical fast-feedback climate sensitivity allows water vapor, clouds, aerosols, sea ice, and all other fast feedbacks that exist in the real world to respond naturally to global climate change.

Climate sensitivity varies as Earth becomes warmer or cooler. Toward colder extremes, as the area of sea ice grows, the planet approaches runaway snowball-Earth conditions, and at high temperatures it can approach a runaway greenhouse effect (8). At its present temperature Earth is on a flat portion of its fast-feedback climate sensitivity curve.

The calculation above is for a long period of time and includes all the slow feedbacks, so I do not know why Hansen calls it a fast feedback. Since the greenhouse gas portion is about half of the total forcing (ie. 1 + 1 = 2), if you consider them the cause (or at least the main feedback) then you get a GHG sensitivity of about 6 degrees. With ice sheets pushing below 45 degrees of latitude, this looks close to a snowball-Earth condition which has a high climate sensitivity. Luckily the same thing was not also happening in Asia, or we might no be here to write about it. A look at the <a href="http://commons.wikimedia.org/wiki/Image:Five_Myr_Climate_Change.png">increasing temperature response</a> to the same orbital forcings as average temperature dropped shows that climate sensitivity became significantly larger during the Pleistocene ice ages.

I am surprised that Hansen did not use the Pliocene (about 3 million years ago) as a benchmark. Here we have CO2 levels around 400 ppm, global average temperature about 2 or 3 degrees higher, and sea levels 25 to 35 meters higher (think ten storey building). The carbon dioxide forcing is about the same ( 280 ppm Interglacial / 180 ppm LGM is close to 400 ppm Pliocene / 280 ppm Interglacial ) for a temperature change about half as much, implying a much lower climate sensitivity, closer to three degrees rather than six for the period we are about to enter.

I still do not think you can use the temperature (or CO2 level) for the initialitation of glaciation to be the same as that sufficient to melt the ice cap. For a large continent like Antarctica I think it will take a few extra degrees to overcome the thermal inertial of all that ice, unless someone can demonstrate why ths is wrong.

Greenhouse Effect

Electromagnetic radiation has two properties - wavelength and intensity.

-------------------
306  http://www.realclimate.org/index.php/archives/2007/05/the-weirdest-millennium/#comment-34515
There are two major effect of changing temperature. The first is to change the distribution of ground vibrational level quantum states, which changes the opacity of the system as a function of photon frequency. The second is to change the thermal distribution of population in the first excited level of the two degenerate bending modes, which means that the intensity and frequency distribution of the emission changes.

309: At low temperature and pressure, there is less opportunity for molecules to collide with one another (think top of the atmosphere). At higher pressures and temperatures, the molecules are more likely to interact, which leads to a broadening of the absorption lines.

291: the absorption per molecule at line center is HIGHER for colder molecules.

331: But then there is also the blurring of the spectra at higher pressures. This is due to the fact that these molecules which are absorbing and re-emitting radiation are in motion as a result of their temperatures, colliding and either losing some amount of energy or gaining some amount of energy prior to absorbtion or re-emission - and as such more or less energy will be required to enter either the excited or grounded state.

Visible sunlight penetrates easily through the air and warms the Earth's surface. When the surface emits invisible heat radiation, some of it is absorbed by CO2 in the middle levels of the atmosphere. Thus some energy transfers into the air itself, rather than escaping directly into space. Not only is the air thus warmed, but also some of the energy trapped there is radiated back to the surface, warming it further.

443: Vibrational radiative lifetimes are very long, seconds. Collisional lifetimes at atmospheric pressure are of the order of 1-10 microseconds. However, the amount of energy necessare to excite a CO2 bend (~600 cm-1) is about 3x the average energy of a collision at 300 K (~200 cm-1) so about 5% of all CO2 molecules at 300 K are excited, just not the same ones at any instant. This is a steady state problem.

458: I don't think absorption of a photon affects the molecule's bond energy per se; what it does is kick an electron of one atom in that molecule to a higher, less stable level. The molecule will then lose energy either by radiating or by hitting another molecule.

adds 4 Watts per square meter to the planets radiation balance for doubled CO2. That's only about a percent of the solar energy absorbed by the Earth, but it's a highly important percent to us! After all, a mere one percent change in the 280 Kelvin surface temperature of the Earth is 2.8 Kelvin (which is also 2.8 Celsius).

Re #<a href=""></a>:

Greenhouse Effect References:
• These lecture notes treat the atmosphere as a constant temperature black body, and claim a greenhouse effect factor of  1.189 x 255 K = 303 K.
• RealClimate discussion - Learning from a Simple Model.
• Real Climate: CO2 colliding with itself in a tube of pure CO2 broadens the lines about 30% more than does CO2 colliding with N2 or O2 in air.
• Ray Pierrehumbert in Real Climate - Busy Week for Water Vapor
• Spencer Weart - Simple Greenhouse Models and an overview of the historical development.
• CO2 is cycled through the atmosphere in a period of about 7.5 years. See: http://www.whrc.org/carbon/index.htm Where it all goes to is not known http://www.whrc.org/carbon/missingc.htm but much of it gets transported to the deep ocean by the thermohaline circulation. That is replaced by CO2 that has remained in the deep ocean for around 1000 years, which is depleted in C14.
• the lapse rate generally increases with altitude in the troposphere. It starts out at about 4.75 K/km near ground level and increases to almost 9.8 K/km near the tropopause. The average is around 6.5 K/km.
• Water vapor at 1% corresponds to about 60% relative humidity at 15 °C [ref]
• Roger Pielke: Relative Roles of CO2 and Water Vapor in Radiative Forcing + comment: "...it is clear that the value of 3.7 Watts per square meter for doubling is not correct."
• water vapor is roughly eight times more effective than carbon dioxide as a greenhouse gas (Hartmann 1994). [nasa]
• Wikipedia - Most of the infrared absorption in the atmosphere can be thought of as occurring while two molecules are colliding. The absorption due to a photon interacting with a lone molecule is relatively small.
• wiki - carbon dioxide is a linear molecule, but it has an important vibrational mode in which the molecule bends with the carbon in the middle moving one way and the oxygens on the ends moving the other way, creating some charge separation, a dipole moment, thus carbon dioxide molecules can absorb IR radiation. Collisions will immediately transfer this energy to heating the surrounding gas. On the other hand, other CO2 molecules will be vibrationally excited by collisions. Roughly 5% of CO2 molecules are vibrationally excited at room temperature and it is this 5% that radiates.
• http://en.wikipedia.org/wiki/Emission_line
• Science: The global warming feedback is based on the fact that cold air radiates less than warm air; if water vapor increases and is distributed to higher, colder altitudes, less heat is radiated to space and thus climate warms.
• [ref] Water absorbs the Infrared Radiation incoming from Sun because the frequency of the internal vibration of the water molecules is the same frequency of the waves of the solar Infrared Radiation. This form of Radiative Heat transfer is known like Resonance Absorption
Weart:
• The Earth must radiate back into space as much total energy as it receives, to stay in equilibrium. Adding gas to the atmosphere moves the site of this emission to higher levels, which are colder. Cold things radiate less than warm ones, so the system must warm up until it can radiate enough.
• When the surface emits invisible heat radiation, some of it is absorbed by CO2 in the middle levels of the atmosphere. Thus some energy transfers into the air itself, rather than escaping directly into space. Not only is the air thus warmed, but also some of the energy trapped there is radiated back to the surface, warming it further.

Questions:
• Does Kirchhoff's Law apply to a greenhouse gas?  The gas will absorb radiation at certain frequencies, and radiate at the same frequencies.  It does not act like a black body.
• Is there any validity to the idea that when a greenhouse gas molecule absorbs radiation, this induces vibration which transfers motion, thus heat, to the surrounding atmosphere?  Does this process happen in reverse, ie, a collision induces a vibrational state which causes the GHG to emit a photon?
• Does the Stefan Boltzmann law apply to intensity of radiation emitted by a greenhouse gas at a certain temperature?
• How much effect is there from atmospheric pressure causing the absorption spectrum of a greenhouse gas to broaden?
• Can the downwelling longwave radiation be measured at the surface? Can we tell from the wavelength which greenhouse gas it came from?  Reference?
The Reflector:

This model recognizes that when a greenhouse gas absorbs radiation, it re-radiates it in all directions, including up and down. Greenhouse warming is caused by the portion of longwave radiation that is returned to the surface. Adding more greenhouse gas reduces the amount of radiation that is prevented from leaving the Earth and is instead returned to the surface. More of the greenhouse effect takes place higher in the atmosphere where the ratio of carbon dioxide to water vapor is higher, implying that carbon dioxide is a relatively more important greenhouse gas than in the first model.

The average mass of the atmosphere is about 5,000 trillion metric tons or 1/1,200,000 the mass of Earth. According to the National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480×1018 kg with an annual range due to water vapor of 1.2 or 1.5×1015 kg depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27×1016 kg and the dry air mass as 5.1352 ±0.0003×1018 kg." [wikipedia]

Table of Greenhouse Gas Forcings

The largest and most certain change in radiative forcing since the pre-industrial period is an increase of about 2.4 W/m2 due to an increase in well-mixed greenhouse gases (Chapter 6, Figure 6.8 and Table 6.1). Radiative forcing here is taken to be the net downward radiative flux at the tropopause (see Chapter 6). Smaller, less certain contributions have come from increases in tropospheric ozone (about 0.3 W/m2), the direct effect of increases in sulphate aerosols (about -0.4 W/m2) and decreases in stratospheric ozone (about -0.2 W/m2). [IPCC]
.
Forcing Agent Forcing (W/m2) Error
Carbon Dioxide 1.46
Methane 0.48
Nitrous Oxide ( N2O) 0.15
Halocarbons 0.35
TOTAL well mixed greenhouse gases +2.43 10%
Stratospheric O3
-0.15
67%
Tropospheric O3
+0.35
43%
Direct sulphate aerosols
-0.40
200%
Direct biomass burning aerosols
-0.20
300%
Direct FF aerosols (Black Carbon)
+0.20
200%
Direct FF aerosols (Organic Carbon)
-0.10
300%
Direct mineral dust aerosols
-0.60 to +0.40
Indirect aerosol effect  {1st effect only; all aerosols}
0 to -2.0
Land-use (albedo)
-0.20
100%
Solar
+0.30
67%
TOTAL

...back to main page

African Climate Change in 10,000 Years

The vegetation of Africa is compared for 8,000 years ago, during the mid-Holocene warming when it was about a degree or two warmer, with today. [ref]  A warmer climate is clearly a wetter one.  Forested areas expand, and climate zones shift away from the equator. Note that the Sahara was not a desert at all (the yellow is grassland, not desert).  The temperature difference is well within the range predicted to occur during the 21st century due to global warming.  Does the map on the left show what the consequence will be?

Not right away, at least.  The paleoclimate data is from a climate in equlibrium, while the near future will be a climate in transition.  There are several reasons while it may take some time to reach equilibrium rainfall levels
• The ocean does not warm as quickly as the land.  Moisture levels are largely determined by sea surface temperature, which lags behind land temperature.  A warmer landmass on its own tends to increase the evaporation rate, which could lead to drying.
• Rainfall is also influenced by existing vegetation.  Increased vegetation generates more rainfall, in a positive feedback loop.  But it takes time for vegetation to establish itself.

Paleoclimate Stuff

[ref] The record obtained at these sites allowed us to evaluate the causes and effects of several major global events in Earth history, including:

1. Demonstrating that the latest Cenomanian-Turonian (C/T) ocean anoxic event was unrelated to sea-level change on million-year or 100-k.y. scales.
2. Suggesting that a major cooling spanning the Campanian/Maastrichtian boundary was associated with a sea-level lowering and inferred ice volume increase.
3. Correlating a latest Maastrichtian global warming with Deccan trap volcanism.
4. Linking the marine mass extinctions at the end of the Cretaceous with ballistic ejecta. In addition, we showed that collapse of the vertical isotopic gradient ("Strangelove Oceans") extended to neritic environments and that there was minimal change in sea level associated with the Cretaceous/Tertiary (K/T) boundary.
5. Establishing that low 13C and 18O and high kaolinite values were associated with the Paleocene/Eocene thermal maximum (PETM) in NJ neritic sections and that isotopic values remained low and kaolinite remained high throughout a thick section above the carbon isotope excursion (CIE). This reflects either that warmer and wetter climate persisted for >300-400 k.y. in NJ (unlike deep-sea records that show an exponential return to pre-PETM conditions after ~200 k.y.) or that the extremely rapid deposition of this section occurred in response to a cometary impact.
6. Showing that a large (~60 m), earliest Oligocene drop in sea level was associated with development of an ice sheet equivalent in size to the modern East Antarctic ice sheet, though sea level again rose by nearly 50 m ~1 m.y. later, suggesting near collapse of the ice sheet. The ice sheet subsequently grew and decayed numerous times in the Oligocene-middle Miocene.

Greenland Ice Balance

Summing best estimates of the various mass balance components for Greenland gives a balance of –8.5 ± 10.2% of the input, or +0.12 ± 0.15 mm/yr of global sea level change, not significantly different from zero. [IPCC 2001]  See also IPCC prediction for the future.

North Atlantic Oscillation

Strong positive phases of the NAO tend to be associated with above-averagel temperatures in the eastern United States and across northern Europe and below-average temperatures in Greenland and oftentimes across southern Europe and the Middle East. They are also associated with above-average precipitation over northern Europe and Scandinavia in winter, and below-average precipitation over southern and central Europe. Opposite patterns of temperature and precipitation anomalies are typically observed during strong negative phases of the NAO. During particularly prolonged periods dominated by one particular phase of the NAO, anomalous height and temperature patterns are also often seen extending well into central Russia and north-central Siberia. [ref]

No positive correlation between arctic SAT and the NAO before 1950 is found – in fact, here we find that the correlation is negative (r ~ -0.39). [Nansen]

An Example of Visually Inflating Climate Data

The figure below shows the change in the melt extent of the Greenland ice cap between 1992 and 2002. This figure was used in the Arctic Climate Impact Assessment, by James Hansen in this paper, and by Al Gore in "An Inconvenient Truth". There are two reasons it is misleading:
• The concept of "melt extent" does not refer to a net loss of ice, as one might think. Instead it is defined here as "experiencing at least 1 melt day between April 1 - September 25". This metric is used because liquid water absorbs energy differently than ice and snow, making it easy to detect from satellites. So the red area is not actually melting, it just means it got warm enough for liquid water to appear at least one day that year.
• The dates 1992 and 2002 have been chosen (ie. cherrypicked) to select the lowest and highest values on record. 1992 was the year after the Mount Pinatubo volcanic eruption, which caused global cooling. The green line on the graph (drawn by me) shows the rate of increase presented on the maps, which is many times greater than the actual average rate of increase, shown by the red line.

Approximately 98% of the energy supplied annually to the Arctic system is advected from lower latitudes by the atmosphere [Nakamura and Oort, 1988]. [98% of what? This can't include the average 100 w/m2 solar insolation.]  Models predict (and observations seem to confi rm) that warming is enhanced in the Arctic [Arctic Climate Impact Assessment, 2005]. Consequently, the meridional poleward temperature gradient may decrease and reduce the northward transport of sensible heat into the Arctic (heat that is associated with the physical temperature of air parcels).  This negative feedback could slow the transition to the new state, but a compensating increase in the poleward transport of latent heat may occur (heat stored as water vapor, which is released upon condensation). Thus, changes in energy transport from lower latitudes provide no definite brake on the system.

Arctic cloud cover might also slow the warming: Cloud cover is decreasing in winter and increasing in other seasons [Wang and Key, 2003]. Over ice-covered areas, however, the shading effect will be small owing to low surface-cloud contrast in refl ectivity, and thus additional clouds should enhance longwave emission and warm the surface [Shupe and Intrieri, 2004]. Therefore, cloud-radiation feedbacks are not expected to derail the Arctic’s trajectory.
[ref]

If warming stabilises at 3 degrees Celsius, the ice sheet could survive for several thousand years. But if temperatures rise by 8 degrees Celsius, which several scenarios predict, then it would disappear in 1000 years.

Advection is the result of extensive cooling, sort of like a thermal engine where cold and warm air is continuously exchanged, this process slows down when the Arctic is warmer.  The Arctic cools down substantially depending on how much heat is lost especially during the long night, it is an ideal location for determining Global Warming trends because of wider temperature discrepancies caused by apparently minor (CO2) changes.

Annual mean incoming solar radiation north of the Arctic circle is 100 W/m2, most of it between the spring and autumn equinoxes.

In summer the energy supply to the arctic climate system is controlled by absorbed solar radiation, whereas in winter the arctic energy budget is dominated by advection from lower latitudes.

Antarctica

For Antarctica (Table 11.6), the ice discharge dominates the uncertainty in the mass balance of the grounded ice sheet, because of the difficulty of determining the position and thickness of ice at the grounding line and the need for assumptions about the vertical distribution of velocity. The figure of Budd and Smith (1985) of 1,620x1012 kg/yr is the only available estimate. Comparing this with an average value of recent accumulation estimates for the grounded ice sheet would suggest a positive mass balance of around +10% of the total input, equivalent to -0.5 mm/yr of sea level. [IPCC 2001]

Melting of all existing glaciers and ice caps would raise sea level by 0.5 m (Table 11.3). For 1990 to 2100 in IS92a, the projected loss from land-ice outside Greenland and Antarctica is 0.05 to 0.11 m (Table 11.12).  [IPCC 2001]

Arctic Temperature and Sea Ice Changes

Hovmöller diagram indicating the time–latitude variability of surface air temperature (SAT) anomalies north of 30°N, 1891-1999: (a) Observed

This image shows the difference between 2005 surface air temperatures in degrees Celsius (averaged for January through August) and the fifty-year mean (1955-2004) for the same months. The preponderance of positive values indicates an unusually warm Arctic in 2005. (NCEP/NCAR Reanalysis; NOAA-CIRES Climate Diagnostics Center )  [Return to Press Release]

Arctic Temperature and Sea Ice Extent

Satellite data suggest a net decrease in Arctic ice extent of about 2.9 percent per decade. [ref]

The following two graphs are taken from the 2004 Arctic Climate Impact Assessment paper.  The temperature graph shows a linear rise from 1900 to 1940, a drop from 1940 to 1970, and a rise from 1970 to 2000.  The slope of both the rise and fall is about the same.  The sea ice graph shows no change between 1900 and mid century, then what looks like a linear decline.  The decline in summer starts around 1950, while the winter decline takes until 1970 to begin.
• Why does the temperature rise in the early part of the century have no affect on sea ice extent?
• Why does the decline in summer sea ice extent begin in 1950, while the cooling trend does not reverse itself until 1970?
• Why does the caption attached to the graph suggest the change in sea ice extent is accelerating?  A regression taken from 1900 will give an exponential curve.  But visually at least, the decline seems to start abruptly, and looks linear after that.

These maps show the difference between “normal” sea ice extent (long-term mean), and the year indicated. The long-term average minimum extent contour (1979-2000) is in magenta. The ice extent for each year is shown by the edge of the colored region; within that extent, color bands show differing levels of sea ice concentration. Blue indicates areas where concentration is more than the long-term mean; red shows areas where concentration is less than the long-term mean. The 2005 map shows a marked reduction in extent over the past four years, all of which were also below average.

In 2002 and 2003, the ice pack also experienced much lower concentrations during the minimum, especially true north of Alaska. However, the ice cover has been much more compact during the minimums of 2004 and 2005, yielding small negative or even positive ice concentration anomalies within the ice pack.

Sea Ice extent is a measure of the area that contains at least 15 percent ice. Ice concentration is the fraction of the actual area covered by ice compared to the total area, measured in terms of percentage ice cover. The satellite does not pass directly over the North Pole; this lack of data is indicated by the gray circle in each image.
Access 1980 and 2005 images for print and online use.

Ice cap sizes

North America

Ice volume in this subset of tests spans a range of 28.5-38.9 x 10[1][5] m[3] at LGM, with a predominant cluster at 32-36 x 10[1][5] m[3]. Taking floating ice and displaced continental water into account, this corresponds to 69-94 m eustatic sea level (msl). More than 75% of the accepted tests fall in the range 78-88 msl. We argue that this is a plausible estimate of the volume of water locked up in the NAIS at LGM. [ref]

For our standard run we find a maximum ice volume of 57 × 106 km3 at 18.5 ka cal BP. This corresponds to a eustatic sea level lowering of 110 m after correction for hydro-isostatic displacement and anomalous ice resulting from defects in the specified boundary conditions of the Paleoclimate Model Intercomparison Project (PMIP) for which the UKMO GCM results were generated. Of this 110 m, 82 m was stored in the North American ice sheet and 25 m in the Eurasian ice sheet.  [ref]

Antarctica

At glacial maximum, ice sheets buried almost the entire land surface of Antarctica and extended across the continental shelf, depositing sediment on the continental shelf, slope and rise. Sea level was some 120-135 m lower than today, with 12-26 m of this locked up in the Antarctic ice sheet. Since glacial maximum, the ice sheet has thinned by hundreds of metres in some areas and retreated inland as much as 1000 km, leaving its imprint on mountain ranges and on the seabed, and a detailed history in marine sediments.  [ref]

[ref]

Paleo Sea Level in the Holocene

The general pattern seems to be sea levels rose to a maximum of 2 or 3 meters around 5,000 years ago, and gradually declined after that. This matches the temperature chart for the time period. This water can only come from significant melting of the Greenland and/or West Antarctic ice caps.

The missing value is the actual global average temperature, but it is probably not more than one or two degrees above today, within range of what global warming can lead to in this century. But unlike today the temperature changed gradually over thousands of years. So a tentative conclusion is global warming could lead to ice cap melting, but we do not know how long it would take. This is much the same message as from the Eemian interglacial data.

 Date (BP) Sea Level Rise Location (link to paper) 2,720 1 m northwest coast of Australia 5,000 - 5,800 2.5 - 4 m Brazil 7,400 - 2,000 1 - 1.5 m southeast coast of Australia 7,700 0 8,000 -3 m 8,500 -5 m 10,000 -10 m southeast coast of Australia

A Climate Model for the Twentieth Century

Weather forecasts take today’s situation and calculate how it will evolve over the next few days. They are initial value problems. Climate models do not assimilate current data but instead produce changes in climate as a function of changing boundary conditions, and thus are a boundary value problem - that is not the same as a forecast (which would require an estimate of the ‘weather’ component as well as the climate component). If you know anything about differential equations, you know those are fundamentally different kinds of problems. [ref]

The four-member ensemble mean (red line) and ensemble member range (pink shading) for globally averaged surface air temperature anomalies (°C; anomalies are formed by subtracting the 1890–1919 mean for each run from its time series of annual values) for all forcing [(volcano + solar + GHG + sulfate + ozone)]; the solid blue line is the ensemble mean and the light blue shading is the ensemble range for globally averaged temperature response to natural forcing calculated as a residual [(volcano + solar)]; the black line is the observations after Folland et al. (2001). Taken from Meehl et al. (2004).

Smoothed, zonal mean anomalies of surface temperature (in K) for the observations in each latitude band from 1890-1999. Anomalies are relative to the 1961-1990 climatology. SOURCE: Delworth and Knutson (2000).

1940s-1970s cooling is a combination of increasing aerosols, increasing volcanoes (particularly Mt. Agung in 1963) and a slight decline in solar forcing, overcoming a relatively slow growth in greenhouse gases. [ref]

Model simulations for the future are called projections, not predictions. No-one in this game ever thinks they are predicting the future, although it often gets translated that way in the popular press. We take assumptions that people have made for the future and see what consequences that would have for the climate.

Why the 1940-1970 cooling?  Two abrupt dips, in 1940 and 1960.
Sulphur emissions increased steadily until World War I, then levelled off, and increased more rapidly in the 1950s, though not as fast as greenhouse gas emissions. [ref]

Volcanic Eruptions

Major volcanos:  None line up with 1940 and 1960.

 Date Location Lava and Ash Aerosol (Sulphur) Global Temperature 16 ± 1 My Roza flow of the Columbia River Flood Basalt 576 Tg S 640 Ky Lava Creek Tuff of the Yellowstone Caldera 1000 km3 lava 1783 Grimsvotn (Laki or Lakagigar), Iceland 15.1 km3 lava 122 Tg SO2 -1.3 °C across Euope and N. America 1815 Tambora, Sumbawa, Indonesia 160 km3 ash 1835 Cosiguina, Nicaragua 1875 Askja, Iceland 1883 Krakatau, Indonesia 20 km3 ash 1886 Okataina (Tarawera), North Island, New Zealand 1902 Santa Maria, Guatemala 1907 Ksudach, Kamchatka, Russia 1912 Novarupta (Katmai), Alaska, US 1919 Kelut     Indonesia 1930 Merapi Indonesia 1937 Rabaul Caldera  Papua New Guinea 1951 Lamington, Papua New Guinea, 1951 Hibok-Hibok,  Philippines 1963 Agung, Bali, Indonesia 1980 Mt. St. Helens, Washington, US 1982 El Chichòn, Chiapas, Mexico 2.5 km3 ash 1985 Nevado del Ruiz, Colombia 1991 Mt. Pinatubo, Luzon, Philippines 11 km3 ash

from Large Holocene Eruptions

Natural Forcings (from IPCC)
-3 Wm-2 (for El Chichon and Mt. Pinatubo eruptions)

WIthout the re-supply of CO2 from geological sources incuding volcanic degassing, it has been calculated that removal of CO2 from the atmosphere by silicate weathering, carbonate deposition and the burial of organic matter could potentially deplete to CO2 content of the pre-industrial atmosphere in 10,000 years, and the atmosphere-ocean system in 500,000 years. [ref]

CO2 flux at Marine Ocean Ridges is estimated to be 66 to 97 Mt / year.  This appears to be balanced by the sink provided by hydrothermal alteration of newly formed ocean floor lavas.

Beginning of a Simplified Climate Model

CS = Climate Sensitivity = 2.7
CA = carbon content of atmosphere, in ppm
CAR = CO2 increase rate in atmosphere
GE = greenhouse gas emission rate = 1.6%
AA = atmosphere absorption percentage = 0.58%
E = Carbon emission rate

CAR = E * AA
CA(n) = CA(1970) * (1 + rate) ^ years

1970:  E = 4 Gt C / yr = 1.9 ppm / yr,  CAR = 1.3 ppm / yr;  CA = 325 ppm;  T = 14.0
2005 =  E = 7.5 Gt / yr = 3.5 ppm/yr,  CAR = 2 ppm / yr;  CA = 375 ppm;  T = 14.5
2100 (IPCC B1)  T = 15.6

Regional Amplification
Ocean = 0.7
45 deg. N = 1.5
60 deg. N = 2.5

Relationship of Hurricane Intensity with Global Warming

Other factors being equal, hurricane intensity increases by about 5% for each degree of increase in sea surface temperature.

...an estimate of a 5%–10% increase in maximum wind speeds for a 2°C change in SST. The increase in intensity found by WHCC is equivalent to a 5% increase in maximum wind speeds for a 0.5°C SST increase, which is a factor of 2–4 larger than that estimated from theory and determined from the model simulations of Knutson and Tuleya (2004). Recent simulations using the Japanese Earth Simulator (Oouchi et al. 2006) found a 10.7% increase in intensity for a 2.5°C increase in SST, which scales linearly to a 2.1% increase in intensity for a 0.5°C increase in SST, which is approximately a factor of 2 smaller than the increase found by WHCC. [Ref]

The observed SST increases in the Atlantic and Pacific tropical cyclogenesis regions range from 0.32°C to 0.67°C over the 20th century.  [ref]

The temperature gradient that matters for hurricanes is the difference between the sea surface and the top of the troposphere, and if the vertical structure breaks down due to wind shear the hurricane dissipates or won't form.

Mid Latitude Storms

The factors that control this are often confounding and so make this a tricky prediction. Simple arguments based on the expected 'polar amplification' and the fact that the surface temperature gradient between the tropics and the poles will likely decrease would reduce the scope for 'baroclinic instability' (the main generator of mid-latitudes storms). However, there are also increases in the upper troposphere/lower stratospheric gradients (due to the stratosphere cooling and the troposphere warming) and that has been shown to lead to increases in wind speeds at the surface. And finally, although latent heat release (from condensing water vapour) is not a fundamental driver of mid-latitude storms, it does play a role and that is likely to increase the intensity of the storms since there is generally more water vapour available in warmer world. It should also be clear that for any one locality, a shift in the storm tracks (associated with phenomena like the NAO or the sea ice edge) will often be more of an issue than the overall change in storm statistics. [RealClimate]

Solar Driven Climate Change

The Solar constant above Earth's atmosphere is 1368 W/m2  ± 0.1%, possibly related to sunspots. But most of that radiation reaches the Earth's surface obliquely, and half of the Earth is in darkness. The mean solar energy reaching the Earth's surface is 265 W/m2.
• These satellite instruments suggest a variation in annual mean TSI of the order 0.08% (or about 1.1 W/m2) between minimum and maximum of the 11-year solar cycle. [IPCC 6.11]
• Solar irradiance change has a strong spectral dependence [Lean, 2000], and resulting climate changes may include indirect effects of induced ozone change [RFCR; Haigh, 1999; Shindell et al., 1999a] and conceivably even cosmic ray effects on clouds [Dickinson, 1975]. Furthermore, it has been suggested that an important mechanism for solar influence on climate is via dynamical effects on the Arctic Oscillation [Shindell et al., 2001, 2003b]. [ref]
• Time-dependent experiments produce a global mean warming of 0.2 to 0.5°C in response to the estimated 0.7 W/m2 change of solar radiative forcing from the Maunder Minimum to the present. (from IPCC 2001). But, from IPCC 2007:  Changes in solar irradiance since 1750 are estimated to cause a radiative forcing of +0.12 [+0.06 to +0.30] W/m2, which is less than half the estimate given in  IPCC 2001.
• A U.S. National Academy of Sciences panel estimated that if solar radiation were now to weaken as much as it had during the 17th-century Maunder Minimum, the effect would be offset by only two decades of accumulation of greenhouse gases. As one expert explained, the Little Ice Age "was a mere 'blip' compared with expected future climatic change." [ref]
• A half of a percent change in solar output could raise temperatures, eventually [over a century], about three-quarters of a degree Celsius, which, coincidentally, roughly equals the observed warming in the past century,” says Hansen. [ref]

Solar Forcing Since 1600 (from Lean and Rind, 1998)

Compared are decadally average values of the Lean et al. (1995b) reconstructed solar total irradiance (diamonds) from Fig. 13 and NH summer temperature anomalies from 1610 to the present. The solid line is the Bradley and Jones (1993) NH summer surface temperature reconstruction from paleoclimate data (primarily tree rings), scaled to match the NH instrumental data (Houghton et al. 1992) (dashed line) during the overlap period.

From [ref]

The GCR flux incident on Earth’s atmosphere is modulated by three processes:
a) variations of the solar wind within the heliosphere (on 10–1000 yr timescales, and possibly longer)
b) variations of Earth’s magnetic field (100–10,000 yr)
c) variations of the interstellar flux outside the heliosphere (>10 Myr).

On reaching Earth, cosmic rays must traverse the geomagnetic field to reach the lower atmosphere. In consequence, the GCR intensity is about a factor 4 higher at the poles than at the equator, and there is a more marked solar cycle variation at higher latitudes.

The GCR flux over these different timescales varies by between 15% during the 11 yr solar cycle, to as much as a factor 2 increase during periods of low geomagnetic field and low solar activity. Interstellar modulations of the GCR flux are estimated to be between -75% and +35% of present values [28] on cosmological timescales, corresponding to the 140 Myr crossing period of the solar system with the spiral arms of the MilkyWay (where the peak fluxes probably reside). Nearby supernovae could increase the GCR fluxes above these values. In summary, if the cosmic ray-climate connection is causal, then the climate appears to be remarkably sensitive to quite small secular changes of GCR intensity—of around 10% or so.

[How can] an energetically-weak GCR signal (which is roughly equivalent to that of starlight) is amplified into a significant climate forcing.

Distribution of Energy Use

Canada’s GHG Emissions by Sector, End-Use and Sub-Sector
Including Electricity-Related Emissions
2004
Total GHG Emissions Including Electricity (Mt of CO2e)   505.4

Residential (Mt of CO2e)   76.7
Space Heating   41.3
Water Heating   19.2
Appliances   11.5
Major Appliances   7.0
Other Appliances   4.5
Lighting   4.0
Space Cooling   0.8

Commercial/Institutional (Mt of CO2e)   67.9
Space Heating   34.1
Water Heating   5.7
Auxiliary Equipment   10.2
Auxiliary Motors   6.0
Lighting   7.1
Space Cooling   4.2
Street Lighting   0.5

Industrial (Mt of CO2e)   169.7
Mining   37.8
Pulp and Paper   23.4
Iron and Steel   17.7
Smelting and Refining   15.5
Cement   4.7
Chemicals   10.6
Petroleum Refining   22.3
Other Manufacturing   31.6
Forestry   1.8
Construction   4.1

Total Transportation (Mt of CO2e)   176.4

Passenger Transportation (Mt of CO2e)   94.3
Cars   43.8
Light Trucks   30.1
Motorcycles   0.2
Buses   3.6
Air   16.5
Rail   0.2

Freight Transportation (Mt of CO2e)   75.4
Light Trucks   12.8
Medium Trucks   10.3
Heavy Trucks   36.8
Air   1.1
Rail   5.8
Marine   8.7

Off-Road (Mt of CO2e) d,e   6.6

Agriculture (Mt of CO2e) a,e   14.7

One barrel of oil (42 U.S. gallons, or 159 liters) can provide about 6 million Btu.
CO2 released per barrel of oil (distillate fuel)= 0.47 tons, or 0.003 tons / liter
So a carbon tax of \$30/ton CO2 is about 10 cents per litre.

\$30 / ton CO2 = 7.25 cents per litre [ref]
\$37 per ton of carbon "starter tax" mentioned earlier, equating to around 10 cents a gallon of gasoline

8.8 kg CO2/ US Gal.  [ref]
times 1 gal / 3.785 liters
2.3 kg CO2 / litre

US CO2 emissions
21% Residential - 12% light  40% heat and cool
18% commercial - 20% light   18% heat and cool
28% Industrial

A typical new 1000-MW coal-fired power station produces around 6 million tons of carbon dioxide annually.

The carbon content of natural gas is only 60 percent that of coal per unit of primary energy content.

"When the ‘best guess’ estimates of radiative forcing are applied to global average coal and gas characteristics, the benefits of fuel switching are delayed by about 30 years," Jain said. "The delay is caused by the reduction in sulfate aerosol emissions and increase in natural gas-related methane emissions that occurs when switching from coal to natural gas – creating a net warming effect." [ref]

However, coal and gas use also release methane, the second most important greenhouse gas emitted by human activities. During coal extraction, methane trapped in and around coal seams is released to the atmosphere. Methane also is released whenever natural gas escapes during transportation and distribution. Hence, switching from coal to gas would reduce methane emissions from coal mining, but increase natural gas-related emissions.

Mountain Pine Beetle

Beetles and Cold Weather   [ref]
• Cold weather kills the mountain pine beetle. Mountain pine beetle eggs, pupae and young larve are the most susceptible to freezing temperatures.
• In the winter, temperatures must consistently be below -35 Celsius or -40 Celsius for several straight days to kill off large portions of mountain pine beetle populations.
• In the early fall or late spring, sustained temperatures of -25 Celsius can freeze mountain pine beetle populations to death.
• A sudden cold snap is more lethal in the fall, before the mountain pine beetles are able to build up their natural anti-freeze (glycerol) levels.
• Cold weather is also more effective before it snows. A deep layer of snow on the ground can help insulate mountain pine beetles in the lower part of the tree against outside temperatures.
• Wind chill affects mountain pine beetles, but is usually not sustained long enough to significantly increase winter mortality.

Historical Mountain Pine Beetle Activity

Mountain pine beetle (MPB) has been present in British Columbia's forests for millenia. Foresters have recorded MPB outbreaks in some parts of BC since 1910. However, evidence of MPB activity going back hundreds of years is found in scars on lodgepole pine trees.

Impacts of Climate Change on Range Expansion by the Mountain Pine Beetle

Abstract: The current latitudinal and elevational range of mountain pine beetle (MPB) is not limited by available hosts. Instead, its potential to expand north and east has been restricted by climatic conditions unfavorable for brood development. We combined a model of the impact of climatic conditions on the establishment and persistence of MPB populations with a spatially explicit, climate-driven simulation tool. Historic weather records were used to produce maps of the distribution of past climatically suitable habitats for MPB in British Columbia. Overlays of annual MPB occurrence on these maps were used to determine if the beetle has expanded its range in recent years due to changing climate. An examination of the distribution of climatically suitable habitats in 10-year increments derived from climate normals (1921-1950 to 1971-2000) clearly shows an increase in the range of benign habitats. Furthermore, an increase (at an increasing rate) in the number of infestations since 1970 in formerly climatically unsuitable habitats indicates that MPB populations have expanded into these new areas.

The potential for additional range expansion by MPB under continued global warming was assessed from projections derived from the CGCM1 global circulation model and a conservative forcing scenario equivalent to a doubling of CO2 (relative to the 1980s) by approximately 2050. Predicted weather conditions were combined with the climatic suitability model to examine the distribution of benign habitats from 1981-2010 to 1941-2070 for all of Canada. The area of climatically suitable habitats is anticipated to continue to increase within the historic range of MPB. Moreover, much of the boreal forest will become climatically available to the beetle in the near future. Since jack pine is a viable host for MPB and a major component of the boreal forest, continued eastward expansion by MPB is probable.

Justice Michael Burton on Al Gore's "An Inconvenient Truth"

[from here]

Untruth 1

Gore says: A sea-level rise of up to seven metres will be caused by melting of either West Antarctic or Greenland ice cap in the near future. Cities such as Beijing, Calcutta and Manhattan would be devastated.

Judge says: "This is distinctly alarmist, and part of Mr. Gore's 'wake-up call.' It is common ground that if indeed Greenland melted, it would release this amount of water, but only after, and over, millennia, so that the Armageddon scenario he predicts, insofar as it suggests that sea-level rises of seven metres might occur in the immediate future, is not in line with the scientific consensus."

Untruth 2

Gore says: Low lying inhabited Pacific atolls are being inundated because of anthropogenic global warming. "That's why the citizens of these Pacific nations have all had to evacuate to New Zealand."

Judge says: "There is no evidence of any such evacuation having yet happened."

Untruth 3

Gore says: The shutting down of the "Ocean Conveyor" would lead to another ice age.

Judge says: "According to the Intergovernmental Panel on Climate Change, it is very unlikely that the Ocean Conveyor (an ocean current known technically as the Meridional Overturning Circulation or thermohaline circulation) will shut down in the future, though it is considered likely that thermohaline circulation may slow down."

Untruth 4

Gore says: Two graphs relating to a period of 650,000 years, one showing rise in CO2 and one showing rise in temperature, show an exact fit.

Judge says: "Although there is general scientific agreement that there is a connection, the two graphs do not establish what Mr. Gore asserts."

Untruth 5

Gore says: The disappearance of snow on Mt. Kilimanjaro is expressly attributable to global warming.

Judge says: "The scientific consensus is that it cannot be established that the recession of snows on Mt. Kilimanjaro is mainly attributable to human-induced climate change."

Untruth 6

Gore says: The drying up of Lake Chad is a prime example of a catastrophic result of global warming.

Judge says: "It is generally accepted that the evidence remains insufficient to establish such an attribution."

Untruth 7

Gore says: Hurricane Katrina and the consequent devastation in New Orleans is due to global warming.

Judge says: "It is common ground that there is insufficient evidence to show that."

Untruth 8

Gore says: Polar bears have drowned swimming long distances to find ice.

Judge says: "The only scientific study that either side before me can find is one which indicates that four polar bears have recently been found drowned because of a storm."

Untruth 9

Gore says: Coral reefs are bleaching because of global warming.

Judge says: "The actual scientific view, as recorded in the IPCC report, is that, if the temperature were to rise by 1-3 degrees centigrade, there would be increased coral bleaching and widespread coral mortality, unless corals could adapt or acclimatize."

Two more, from Real Climate

At one point Gore claims that you can see the aerosol concentrations in Antarctic ice cores change "in just two years", due to the U.S. Clean Air Act. You can't see dust and aerosols at all in Antarctic cores — not with the naked eye — and I'm skeptical you can definitively point to the influence of the Clean Air Act.

Another complaint is the juxtaposition of an image relating to CO2 emissions and an image illustrating invasive plant species. This is misleading; the problem of invasive species is predominantly due to land use change and importation, not to "global warming".