The greatest source of climate uncertainty is political, not scientific. We can choose to limit warning, or we can take our chances in a hotter world

Read more: “IPCC 2013: The latest state of the climate report“

THE latest scientific report from the UN Intergovernmental Panel on Climate Change, published last week, was received almost with a shrug. There were no real showstoppers (no surprise, as most of the report had been leaked in advance). Minds were not changed. Battle lines did not budge. Denialists tried to rubbish the report but found themselves preaching only to the converted.

Perhaps the juiciest morsel was the IPCC’s acceptance that warming has slowed since 1998 (see “Climate report: Lull in warming doesn’t mean we’re safe“). Even this has been widely studied and debated elsewhere; the IPCC simply reiterated that the change can be explained as part of the complex interactions between natural and human-made climate effects, with the big picture unchanged. The report is the product of painstaking consensus-building; it is inevitably not cutting-edge.

That is not to say the science is “settled”. Science never is. Many uncertainties and complexities remain to be understood, but the chances that we will discover that we have got the big picture wrong are diminishing day by day. The work of climate scientists is now to fill in ever-finer details. So why are we still so uncertain what the future holds?


The chances of discovering that we have got the big picture wrong are diminishing day by day

The greatest source of uncertainty is not science, but society: the IPCC’s declaration that the world will warm by anywhere between 0.3 and 4.8 °C reflects social and political uncertainties, not scientific ones.Climate scientists study the climate. They cannot tell us how much money will be invested in green energy R&D, whether fertility rates will go up or down, whether we will dig up all the remaining fossil fuels and burn them, or the outcomes of numerous other decisions that affect the atmosphere – though they can tell us what will probably happen if we do or don’t take them (see “Earth, 2100 AD: Four futures of environment and society“).

And so attention must now turn to the next two IPCC reports. The first of these, due out in March 2014, will cover impacts, adaptation and vulnerability; the second, out the following month, will cover mitigation.

As yet there are no leaks from these reports. They are likely to develop the theme that the future is still in our hands. We can choose to limit warming, or continue our carbon bender and take our chances in a world that is around 5 °C hotter. It’s up to us.

This article appeared in print under the headline “The world is in our hands”