What happened to the evidence for man-made global warming?

Cognitive dissonance is the uncomfortable feeling you get when confronted with two contradictory ideas. For example, how can one be skeptical about man-made global warming when there is so much empirical evidence? Climategate has provided a way for some to resolve this issue - simply discredit all the evidence for global warming. By focusing on suggestive quotes from a handful of emails by a small number of climate scientists, it allows one to write off the entire field of climate science as a vast conspiracy. This line of reasoning allows Senator James Inhofe to conclude "This whole idea of global warming, I'm glad that's over. It's gone. It's done. We won. You lost. Get a life!"

This attack on an entire field of science is unprecedented. As historian Spencer Weart puts it, "we've never before seen a set of people accuse an entire community of scientists of deliberate deception and other professional malfeasance. Even the tobacco companies never tried to slander legitimate cancer researchers." One might argue that the stolen emails are being taken out of context and often parsed without scientific understanding. Nevertheless, lest we get bogged down in the details, the broader picture is that Climategate narrowly focuses on the behaviour of a handful of scientists and suggestive inferences about a few pieces of climate data. Somehow this allows skeptics to ignore the entire body of scientific evidence, meticulously accumulated by scientists all over the world. This evidence includes the following independent observations that paint a consistent picture of global warming:

• Our planet is suffering an energy imbalance and is steadily accumulating heat (Hansen 2005, Murphy 2009, von Schuckmann 2009, Trenberth 2009)
• Animal and plant species are responding to earlier springs. Eg - earlier frog breeding, bird nesting, earlier flowering, earlier migration of birds and butterflies (Parmeson 2003)
• The distribution of tree lines, plants, birds, mammals, insects, fish, reptiles, marine invertebrates are shifting towards the poles (Parmeson 2003)
• Arctic permafrost is degrading (Anisimov 2006) plus warming at greater depths in the permafrost (Stieglitz 2003)
• Global sea level rise is accelerating (Church 2006)
• Antarctic ice loss is accelerating (Velicogna 2009), even from East Antarctica which was previously thought to be too stable to lose ice mass (Chen 2009)
• Greenland ice loss is accelerating (Velicogna 2009, van den Broeke et al 2009)
• Glaciers are shrinking globally at an accelerating rate (WGMS 2008)
• Arctic sea-ice loss is accelerating with the loss rate exceeding model forecasts by around a factor of 3 (Stroeve 2007).
• The height of the tropopause is increasing (Santer 2003, press release)
• Jet streams are moving poleward (Archer 2008, Seidel 2007, Fu 2006)
• The tropical belt is widening (Seidel 2007, Fu 2006)
• There is an increasing trend in record hot days versus record cold temperatures with currently twice as many record hot days than record cold temperatures (Meehle 2009, see press release).

The Climategate controversy hasn't even touched upon the empirical evidence indicating that human activity is the cause of recent warming:

• Humans are emitting CO2 at such rates that atmospheric CO2 is at its highest level over the past 800,000 years (Brook 2008). The rate of increase is the fastest in 22,000 years (Joos 2008)
• Satellites measure less infrared radiation escaping out to space at the wavelengths that CO2 absorb energy (Harries 2001, Griggs 2004, Chen 2007)
• Surface measurements find more infrared radiation returning back to the Earth's surface (Philipona 2004), specifically at the wavelengths that CO2 absorb energy (Evans 2006)

One cannot deny that some of the Climategate emails are embarrassing for the scientists involved. Their comments and behaviour shouldn't be swept under the carpet and more transparency in climate science is a good thing. However, using quote-mined emails to disregard an entire scientific field is not the behaviour of people genuinely seeking to understand how our climate works. It is, on the other hand, a stupendous act of cognitive dissonance.

UPDATE 8/12/2009: Things Break has emailed me a few other pieces of evidence I'd overlooked:

• A shift towards earlier seasons (Stine 2009)
• Lake and river ice cover throughout the Northern Hemisphere are freezing later and breaking up earlier (Magnuson 2000, Hodgkins 2005)
• Changes to physical and biological systems across the globe are consistent with warming temperatures (Rosenzweig 2008)
• Cooling and contraction of the upper atmosphere consistent with predicted effects of increasing greenhouse gases (Lastovicka 2008)
• Pitcher-plant mosquitoes are genetically evolving to adapt to shifting seasons (Bradshaw 2001)

UPDATE 11/12/2009: H/T to Drosera for mentioning another study:

• Distribution of plants are shifting to higher elevations (Lenoir 2008)

Posted by John Cook on Monday, 7 December, 2009

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