Understanding IPCC reports

The other night I headed over to the Institute of Physics to hear Professor Jonathan Gregory give a lecture to a packed house on The Physical Science Basis of Climate Change. Prof Gregory is one of those scientists who comes armed with a string of positions (Snr. Scientist at the Walker Institute for Climate System Research, Prof. at the Dept. of Meteorology, University of Reading, Met Office Fellow in the Climate Change Group at the Met Office Hadley Centre, Exeter - I'm sure there are more) that makes you wonder whether he is capable of being in many places and doing many things simultaneously (he is a scientist afterall). He is a man who is precise in his choice of words and concise in his explanations.

So, with that kind of background, it is no surprise that a man of those credentials is also an IPCC lead author. The IPCC (Intergovernmental Panel on Climate Change - the world leading authority on climate change) was established in 1988 to assess scientific, technical and socio- economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation. 2007 brings the completion of the 4th Assessment Report. There are three working groups who compile individual reports for the Assessment Report: Working Group 1 addresses the 'physical science basis', Group 2 the' impacts, adaptation ann vulnerability', Group 3 'mitigation'. Prof Gregory is a lead author for the Working Group 1 (whose report was published February 2007), who were tasked with turning their immense brains, knowledge and analytical skills to the physical science basis of climate change.

Here is how it works:
A core of scientists (Working Group 1 was written by 152 lead authors from over 30 countries and reviewed by over 600 experts) are tasked to assess existing peer reviewed literature on climate change, give information on how confident they are of the calculations, compile the report and a summary for policymakers. It is only after that do the scientists sit down with the government representatives to decide whether the summary correctly reflects the report. The Working Group 1 Summary for Policymakers was approved by officials from 113 governments. So, if you are in doubt as to whether or not climate change is really happening, these are the guys who listen to. They take the hard data, the existing literature, the physical theory, the numerical modelling, the research papers, the observations, the computations, the projections and circulation models - all in all the most up-to-date information - from all over the world. Once this is assessed the IPCC brains provide information on how confident they are of the calculations. It is not opinion, but analysis. And to ensure everyone is talking the same language and understands each other, a calibrated language is used (that in itself took a bit of doing to agree, as you can imagine).

IPCC Calibrated language
very likely > 90% probability
likely > 66%
unlikely < 33%
very unlikely < 10%

Unequivocal Fact: Global Warming is happening
There is one fact which none of the scientists and experts disagree on. The warming of the climate system is unequivocal. This is not contested. The 11 of the past 12 years are the warmest on record (the exception is 1996). So anyone who claims they are still unsure as to whether or not global warming is in fact taking place must surely be privy to some remarkable data that flies in the face of what can only be considered conclusive evidence.

The Greenhouse Effect
The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapor, carbon dioxide, nitrous oxide, and methane, for example) trap energy from the sun. Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF colder. The gases in effect insulate the earth, rather like an invisible blanket. Because of how they warm our world, so the earth heats up underneath - rather akin to the heating up under the glass of a greenhouse - these gases are referred to as greenhouse gases. What is happening is that inside the greenhouse - planet Earth - is beginning to overheat.

Back to Prof Gregory: he gave an array of slides demonstrating the observed changes, and those that have proven consistent with expected (simulated) responses - which also demonstrates that much of the earlier future mappings have been pretty spot on.

Where such changes are inconsistent with other explanations, he explained, attributions can be made. Thus, where natural forcings alone do not explain the variations over the past 50 years, most of the observed increase in globally average temperatures since the mid 20th Century is very likely due to the observed increase in anthropogenic green house concentrations. In other words, there's >90% probability that it's all down to us - increase in temperature has resulted from the influence humans have on the natural world - from the burning of of fossil fuels and deforestation. So, there we have it - we are in all likelihood destroying the very world we live on by our own actions. Using that well worn analogy, if you were told by a medical expert you had >90% chance of dying of cancer very soon unless you stopped smoking now, what would you do? Go with the 10% off-chance that you may be okay? Or take action...

Future Simulations
Such extensive analysis of the changes in ice sheet volume, sea ice, glacier and ice cap reductions, salinity, precipitation, water vapour, green house gases, temperature, ocean heat, sea level rise, thermal expansion etc. has been put to good use. A family of future scenarios (on a business as usual premise) to the end of the 21st Century with a range of increase in temperature between 1 and 4 degrees has been computed. It does not make for pretty viewing. Even on the most optimistic scenario (and the most unlikely) of just one degree increase, does not absolve our responsibility to address what for future generations will bring even higher increases. Increase of temperature may bring positive feedbacks, such as die-back of forests, and with the loss of those sinks comes the release of even more greenhouse gases, contributing to even further and more rapid increase of temperatures.

Future warming of temperatures, in the calibrated language of the ever cautious scientists, is virtually certain, heat waves more frequent, and heavy precipitation very likely. By 2090 it is very likely that there will be no summer sea ice in the Arctic. That's a lot of dead polar bears. As for the cooling of the Gulf Stream from the increased loss of ice? Sudden collapse, as current analysis of the computations stands, is however very unlikely.

We need people like Prof Gregory and all the other lead authors and scientists to make analyse the data for us. I cannot pretend that I understand all of it, but, in the only way I can explain, I am satisfied so that I am sure that these IPCC scientists and experts know what they are talking about. Such data is inevitably our primary materials upon which we must act.

As for impacts, adaptation and vulnerability, and for that matter, mitigation of climate change - well, these two areas are the subject of reports that have been published by Working Group 2 and Working Group 3. What I need now are equally informative lectures on both those reports.

For the 2007 Working Group Reports (1, 2 & 3) go to: ipcc.ch
The reports by the three Working Groups provide a comprehensive and up-to-date assessment of the current state of knowledge on climate change. It is currently finalizing its Fourth Assessment Report "Climate Change 2007", also referred to as AR4 which will be available in November.