The policies of the next governments of the global community need to hear in a loud voice what we the everyman need to tell them. We need the information about the science in clear understandable language that will help us make the right decisions. regarding our future.
The problem with the IPCCâs paper Climate Change 2007: The Physical Science Basis â Summary for Policymakers ( pdf – hereafter referred to as SPM) is that it really needs to be read very carefully and interpreted if not by experts certainly by people with some background and understanding of the literature of climate change. It is not easy reading. For example, when trends are given particular attention needs to be given to the baselines, the intervals and how they are derived. They shift around a bit throughout the document.
Yes, the pictures do tell a story, but not the emotional story we saw on the first episode of the TV series Planet Earth where polar bears swam endlessly looking for sea ice from which to hunt seals. Back on land a tired and hungry large male tried to cull a sea lion cub. Defeated by the size, intelligence and solidarity of these huge animals, injured by their fearsome tusks, the exhausted polar bear lies down to die.
This is science, not emotional anecdotes but solid, conservative science. Science which backs up the science of the Stern Review. What emerges is a global crisis in the making, not quite as scary as the Stern Review, but scary enough. You can reasonably conclude, I think, that the future biosphere is in play.
The IPCC context
The SPM is the first of a series of an IPCC publishing program in 2007 associated with the Fourth Assessment Report. There will be three working party reports:
1. The Physical Science Basis
2. Impacts, Adaptation and Vulnerability
3. Mitigation and Climate Change
Then there will be a Synthesis Report summarising the other three, highlighting robust findings and key uncertainties.
The SPM may be considered unusual in that the summary is issued in February while the report on which it is based is due in May. This does not mean that the supporting science is trimmed to fit the conclusions. It simply means that the full report, already in draft form and unofficially available on the net, is being edited before release.
The full Fourth Assessment Report will cover the same ground as the Stern Review final report, including the economic implications, but the approach is more conservative. I understand the cut off for scientific papers to be considered by WP1 was 2005. The process is one where drafts are prepared and issued for comment (30,000 in this case). Comments are considered and the final draft considered and accepted by the participating governments at a meeting. The process yields full consensus based on the scientific literature at the cut-off date, whereas Stern could go with the flow and include reports of new studies up until the end of the writing process at his own discretion.
Significantly, the likelihood of recent warming being anthropogenically caused has been upgraded from likely (> 66%) in TAR (Third Assessment Report 2001) to very likely (>90%). There are two further categories – extremely likely (>95%) and virtually certain (>99%). I understand that the probability assessment was reduced a notch because of China. Thatâs the way the IPCC process works. They need consensus, not a majority view.
Current concentrations of CO2 (379ppm in 2005) far exceed what is revealed in the ice core record in the last 650,000 years (180 to 300ppm). CO2 from fossil fuels has increased from 6.4 Gt per year in the 1990s to 7.4 in 2000-2005. Thatâs 15.6% up on last decade, so the trend is clear. The graph of the last 10,000 years is more like an ice pick than a hockey stick. It heads stright up at the end.
The extra carbon in the air traps heat in the planetary system, 80% of which is absorbed by the ocean. This leads to a forcing of the climate over and above natural variations.
Solar radiation forcing as a natural variation is less than half the factor found in TAR and is considered to have little relevance.
CO2 forcing has increased 20% from 1995 to 2005.
Net radiative forcing is 1.6 watts per square metre. But this figure would be 2.8 watts (75% higher) if China and others were not doing a sterling job in polluting the planet.
Here there are choices about how you present the statistics. This graph gives an overview of how things have gone from 1850 to 2000. SPM says that there has been a 0.76 increase from the mean of 1850 â 1899 to 2001 â 2005. But if they had taken the 5-year average at about 1920 as the base they could have found the same increase in a shorter time span.
In SPM they say that the linear trend for the last 50 years of 0.13 per decade is nearly twice that of the last 100 years. But the NASA GISS people tell the story differently telling us that:
Global warming is now 0.6Â°C in the past three decades and 0.8Â°C in the past century. â¦[T]here was slow global warming, with large fluctuations, over the century up to 1975 and subsequent rapid warming of almost 0.2Â°C per decade.
And show quite starkly in the graphics where it is happening most â the Arctic, northern latitudes and central Africa. The SPM is more conservative in its presentation.
Still they do tell us that Arctic temperatures have increased at double the global average in the past century and the top of the permafrost layer has increased by up to 3C since the 1980s.
In looking at the future SPM does envisage a 0.2C per decade increase for the next two decades. But future emissions and hence radiative forcings and consequent temperature increases depend strongly on how many people there will be on earth and on what they do. SMS outlines six scenarios of how the future will unfold. These scenarios derive from the IPCC Special Report on Emissions Scenarios, 2000. The box at the end of SPM explaining the scenarios is taken over directly from the TAR. Factors such as the rate of economic growth, population trends, convergence or heterogeneity between human societies, the degree of social equity, the prevalence of the service and information sectors and the carbon intensity of activities vary with each scenario.
Plenty of grist here for economists, sociologists, futurologists and such. Pick your scenario and then read out the likely temperature and sea level rise (Table SPM-3). Here is the read-out for temperature change from 1980 â 1999 (effectively 1990) to 2090 â 2999 (2095):
B1 1.8 (1.1 â 2.9)
A1T 2.4 (1.4 â 3.8)
B2 2.4 (1.4 â 3.8)
A1B 2.8 (1.7 â 4.4)
A2 3.4 (2.0 â 5.4)
A1F1 4.0 (2.4 â 6.4)
The full range is clearly 1.1 to 6.4, but these results are commonly quoted in the press as a range of 1.8 to 4.0 and sometimes compared with the TAR range of 1.4 to 5.8, giving the impression that things are at least not getting any worse and maybe a bit better. Unfortunately this impression is reinforced in the graphic (Figure SPM-5) which doesnât plot the A1F1 scenario and moves the zero line to 2000.
You could get huge arguments about which scenario will be closest but I reckon they are all a bit alarming. Hereâs why.
Stern and James Hansen benchmark their discussion of future temperatures to pre-industrial levels. Hansen considers that dangerous anthropogenic interference (DAI) (pdf) cuts in at 2C above pre-industrial levels. If you want a quick look at what this means go to Table 3.1 in Chapter 3 and Figure 2 in the full executive summary of the Stern Review. Things like the onset of irreversible melting of the Greenland ice sheet, the weakening of natural carbon absorption, a 20 – 30% decrease in freshwater availability to many millions, reduced crop yields in significant areas, destruction of coral reefs, millions subject to coastal flooding and 15 to 40% of all species facing extinction. If you go to 4C things really start to go pear-shaped.
Now go back to the table of temperatures and add at least 0.6C to each value to bring them into line with Stern and Hansen. Thereâs not much on offer below 2C.
SPM has firmed on the notion that a doubling of CO2 (540ppm) will give rise to about 3C temperature change and accept that we should aim to stay below 450ppm. That gives us 35 years if emissions are not increasing. Which they are.
Stern found that to keep CO2 below this level, emissions would have to peak in the next 10 -20 years and fall at a rate of at least 1 – 3% thereafter. The time to act is now. This need for urgent action is implied but not explicit in SPM.
Here the impression has been given to the casual reader with mal-intent that the SPM reduces the upper limit of sea level rise from 88C to 59C. Ian Macfarlane and Malcolm Turnbull both fell for this one, as did Jennifer Marohasy. Nexus 6 has a neat post sorting out Marohasy. The short version is that the IPCC panel decided that there was insufficient refereed literature identifying longer-term trends to establish a scientific consensus on dynamic shifts in ice sheets, as distinct from straight melting. The TAR calculations did include some ice-sheet movement, while the SPM does not.
SPM makes it clear that if we keep on warming, Greenland will eventually melt resulting in a 7 m rise and:
The corresponding future temperatures in Greenland are comparable to those inferred for the last interglacial period 125,000 years ago, when paleoclimatic information suggests reductions of polar land ice extent and 4 to 6 m of sea level rise.
In conclusion we need to remind ourselves that the SPM is but the first of a series of documentation and addresses only the physical science basis of climate change. Discussion of impacts, adaptation, vulnerability and mitigation are still to come. Yet it is clear that we are dealing with a significant existential challenge to the human race, its standard of civilisation and the biosphere generally. Over 200 nation states working separately within their own boundaries and in their own interests is not going to be sufficient. Indeed we may need a new form of political economy, one that privileges the long-term public interest rather than one that is geared to supply (but not satisfy) individual, short to medium term consumer-based wants.
If we find new ways of relating to the planet, to each other (by this I mean the whole human race, dispensing with the notion of the âOtherâ?), to other species then we may in fact achieve a new identity. This may be a necessary condition of the survival of our civilisation.
Finally the above was not intended as a review. Rather I aimed at an introduction to the main ideas and findings, catering also for long-suffering dialup users with a reluctance to follow up links. By now there is plenty about on the internet, of course. As a selection, there is RealClimate with huge commentary thread, Quiggin was out of the blocks early, Tim Flannery on The World Today and Lateline, finally Greame Pearman on the 7.30 Report.