truth in an inconvenient truth?

RealClimate looks at Al Gore's new movie and gives it a qualified thumbs up...

There are a few scientific errors that are important in the film. 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. I was left wondering whether Gore got this notion, and I hope he'll correct it in future versions of his slideshow. 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". Still, these are rather minor errors. It is true that the effect of reduced leaded gasoline use in the U.S. does clearly show up in Greenland ice cores; and it is also certainly true that climate change could exacerbate the problem of invasive species.

Several of my colleagues complained that a more significant error is Gore's use of the long ice core records of CO2 and temperature (from oxygen isotope measurements) in Antarctic ice cores to illustrate the correlation between the two. The complaint is that the correlation is somewhat misleading, because a number of other climate forcings besides CO2 contribute to the change in Antarctic temperature between glacial and interglacial climate. Simply extrapolating this correlation forward in time puts the temperature in 2100 A.D. somewhere upwards of 10 C warmer than present -- rather at the extreme end of the vast majority of projections (as we have discussed here). However, I don't really agree with my colleagues' criticism on this point. Gore is careful not to state what the temperature/CO2 scaling is. He is making a qualitative point, which is entirely accurate. The fact is that it would be difficult or impossible to explain past changes in temperature during the ice age cycles without CO2 changes (as we have discussed here). In that sense, the ice core CO2-temperature correlation remains an appropriate demonstration of the influence of CO2 on climate.

For the most part, I think Gore gets the science right, just as he did in Earth in the Balance. The small errors don't detract from Gore's main point, which is that we in the United States have the technological and institutional ability to have a significant impact on the future trajectory of climate change.

RealClimate is a great resource ... commentary on the science of climatology from folks who actually do it. The replies can be a bit weird as more than a few crackpots jump in, but there is also an attempt at patient education.

Comments

[Minerva Schwartz]

I don't know how Al can so easily compare charts from over 600,000 years - but I do know that according to the Observatory in Armagh Ireland - where they have been studying daily temperature readings since 1795 - it is caused primarily by solar activity.

Still, it could be that satellites go the wrong way through the ozone layer - forcing it's molecules into space instead of resettling in the layer. But then, who would stop using their cell phones, Wi-Fi, and tv ... Al Gore would then be a major contributor!

Resources: Easy read w/graphic
http://news.bbc.co.uk/1/hi/sci/tech/1045327.stm

A bit more comprehensive w/graphics
http://climate.arm.ac.uk/calibrated/airtemp/yellow-textD.pdf

General Resources:
Armagh Observatory Climate and Meteorology Publications

[Amber Brown]

However, in this connection it is significant that each of the 35 errors listed below misstates the conclusions of the scientific literature or states that there is a threat where there is none or exaggerates the threat where there may be one. All of the errors point in one direction – towards undue alarmism. Not one of the errors falls in the direction of underestimating the degree of concern in the scientific community. The likelihood that all 35 of the errors listed below could have fallen in one direction purely by inadvertence is less than 1 in 34 billion.

Error#1 sea level raising "6 m" (20 feet)
The IPCC says the sea-level has increased up to 7 m (23 ft) naturally in the past climate, and would only be likely to happen again after several millennia. In the next 100 years, according to IPCC, these two ice sheets between them will add a little over 6 cm (2.5 inches) to sea level, not 6 m. Gore has exaggerated the official sea-level estimate by 10,000%. The IPCC estimates a sea-level rise of “59 cm” by 2100. This amounts to less than 2 ft, not the 20 ft imagined by Gore. This is the IPCC’s upper estimate, on its most extreme scenario. The IPCC says that temperature would have to be held at more than 5.5 degrees C for several millennia before half the Greenland ice sheet could melt, which would only cause the sea level to rise by 3 m (10 ft). Finally, the IPCC estimates that the likelihood of humans having any influence on sea level at all is little better than 50:50.
Error#2 CO2 "Driving Tempature"
Gore says that in each of the last four warm periods it was changes in carbon dioxide concentration that caused changes in temperature. It was the other way about. Changes in temperature happened before changes in CO2 concentration. Gore had very clearly implied that it was changes in carbon dioxide concentration that had led to changes in temperature. The significance of this error was explained during the court proceedings, and was accepted.

Error#3 Lake Chad Drying up
Gore says “global warming” dried up Lake Chad in Africa. It did not. People taking up too much water and changing agricultural patterns dried the lake, which was also dry in 8500BC, 5500BC, 1000BC and 100BC.He said, “There are multiple stresses upon Lake Chad.” However, the scientific consensus is that at present those “stresses” do not include “global warming.”

Error#4 Hurricane Katrina "Man Made"
Gore says Hurricane Katrina was caused by “global warming.” It was not. It was caused by the failure of Gore’s party, in the administration of New Orleans, to heed 30 years of warnings by the Corps of Engineers that the levees – dams that kept New Orleans dry – could not stand a direct hit by a hurricane. Katrina was only Category 3 when it struck the levees. The levees failed, as the Engineers had said they would. Gore’s party, not “global warming,” was to blame for the consequent death and destruction.

Error#5 Polar Bears dying
Gore says a scientific study shows that polar bears are being killed swimming long distances to find ice that has melted away because of “global warming.” They are not. The study, by Monnett & Gleason (2005), mentioned just four dead bears. They had died in a huge storm, with high winds and waves in the Beaufort Sea. The amount of sea ice in the Beaufort Sea has grown over the past 30 years. A report for the World Wide Fund for Nature shows that polar bears, which are warm-blooded, have grown in numbers where temperature has increased, and have become fewer where temperature has fallen. Polar bears survived the last interglacial period when global temperature was 5 degrees Celsius warmer than now, and there was probably no Arctic ice-cap at all. The real threat to polar bears is not “global warming” but hunting.

Error#6 Japanese Typhoons "set new record"
Gore says that 2004 set a new record for the number of typhoons striking Japan. It did not. The trend in the number of typhoons, and of tropical cyclones, has fallen throughout the past 50 years. The trend in rainfall from cyclones has also fallen, and there has been no trend in monsoon rainfall.

These are only the most important errors I found. 29 are not listed.