climate change forum hits Cape Town

I do find it vaguely curious that the American Association of Petroleum Geologists should hold the AAPG 2008 International Conference and Exhibition in Cape Town, and host a Global Climate Change Forum one evening during the event, financed in part by Shell. I just love how Americans think they can represent the world. (You've heard of American baseball's World Series, right?) Anyway, regardless of the AAPG's motivation, and my cynicism, they did in fact put up a world-class panel of four lead authors of the IPCC 4th Assessment Report of 2007, last night at the CTICC.

None of the four panelists is a climate change sceptic, but they didn't claim there is no controversy or debate around climate modelling or the interpretation of the multitude of data sources for understanding the historic record and forecasting future climate. What they did say was that the science is evolving, and the differences don't negate the clear convergence that is strengthening month by month. There is a huge volume of data constantly being exchanged, checked, integrated and adjusted to provide a cohesive body of work.

Thomas Peterson, of NOAA's National Climatic Data Center in North Carolina, sees it as his job to perform "quality control" functions on the data sets. His team identifies erroneous data through various tests and comparisons, finds ways to fill in gaps in sparse data sets, and adjusts historical data so that they reflect what would have been recorded by modern instruments, so that data is homogenous.

All this adjusting doesn't mean "make the data fit the conclusions", it means making sense of differences in analysis methodologies and data type, source, age, and so on. The extent to which the IPCC reports are peer reviewed is unprecedented - in the normal course of scientific advancement, what individual research paper is reviewed by literally thousands of scientists over a number of iterations?

What this panel pointed out is that there are always data that seem like anomalies, or contradictions, and these generate intense debate, particularly among people outside the process who may see the information as undermining of the IPCC findings on climate change. In most cases, the anomalies can be explained by those who understand the data.

For example, Georg Kaser from Innsbruck, Austria, is an expert in glaciers, and he has generated some heat by pointing out that while most glaciers are shrinking, some are actually increasing in size. What he pointed out last night was that certain glaciers, for different reasons, are more sensitive to changes in rainfall than changes in temperature. This can be because they are in cold climates where warming of a few degrees might have no effect on melting, or because of the particular type of glacier. The glacier behaviour is consistent, however, with the changes in total energy in the system in all its forms - not just measured in terms of temperature.

And while it is now irrefutable that the climate is warming, there are parts of the globe that are cooling - so, for example, there is more sea ice around Antarctica because it is getting colder there.

Some things are still not clearly understood, but the number of mysteries is being relentlessly reduced. Where they remain, that's ok; no model is perfect, and the important thing is to understand its limitations and uses.

Jonathan Overpeck, whose field is paleoclimatology (study of the ancient climate record), pointed out that from the perspective of the ancient record, current greenhouse gas concentrations are far above what would be natural levels without human influence. We are not in a historically warm period, but the rate at which we are changing concentrations of CH4, CO2 and N2O are unprecedented. The record shows that there is good correlation between temperature and GHG levels, but what is worrying is that there is not a clear understanding of what caused some of the very abrupt changes in global temperature. Scientists don't know what might take us over a tipping point that would accelerate our already high rate of change.

125,000 years ago, the Arctic temperature was 3-5 degrees warmer than it is now, and the sea level was 4-6m higher (current investigations are suggesting that the sea may have been as much as 9m higher). We are now on course to bring the Arctic temperatures back to that level, even if we dramatically slow emissions right now.

Bruce Hewitson, director of UCT's Climate System Analysis Group and a Coordinating Lead Author on regional climate change projections for both the IPCC's 3rd (2001) and 4th (2007) Assessment Report, highlighted two key shortcomings of the IPCC's work. One is that Global Climate Models (GCM), while useful, are limited in their ability to help with national and regional responses to climate change. The models are improving all the time, and are useful for what they do, but Prof Hewitson is undertaking groundbreaking work in downscaling the GCMs for regional interpretation. Where the various models differ is not on the overall trends, but on where the regional boundaries are between areas that will show particular changes in future.

At these boundaries, scientists can't be sure what will happen, and governments don't know how to plan for adaptation. Most of the Western Cape, for example, is repesented as one point on a GCM, despite significant variations in temperature and rainfall within the region - the global models just can't reflect teh diversity at this scale. So the UCT team is testing perturbations in the model parameters, to generate a "cloud" of variable outcomes at the regional level. This will help deal with probabilities, which is the best way to respond to uncertainty.

The other limitation that Hewitson sees is that there is no integration between the science and the social challenges we face in responding to climate change. Vulnerability is a function of exposure to risk, the magnitude of the risk, and capacity to respond. Africa faces high exposure to climate-related risk of high magnitude, and has a poor capacity to respond positively. He is taking the modelling forward, since the global models aren't up to the job of regional planning.

Climate change is already happening in Africa. Plants and animals are on the move, and agriculture is under pressure. Hewitson believes that indigenous knowledge can be useful in validating the regional models, but perhaps more importantly in finding ways to improve community resilience and adaptation to change. The big challenge is in gaining access to that knowledge. There are some initiatives, such as weADAPT, that are beginning to find ways to collaborate on adaptation strategies, but we have a long way to go.

Comments

[Pam Sykes]

Thanks for a great roundup, Rory - sounds like an interesting evening, wish I could have been there!