The speed and scope of climate change is now surpassing even the most sobering predictions of the last report of the IPCC.
A new analysis of the latest, peer-reviewed science indicates that many predictions at the upper end of the Intergovernmental Panel of Climate Change’s (IPCC) forecasts are becoming more likely. Some events – such as ocean acidification, losses of glaciers, and shrinking of ice-sheets – thought likely to occur in the long-term are already happening or will happen far sooner than had previously been thought, according to a new report issued by the United Nations Environment Programme (UNEP), entitled “Climate Change Science Compendium 2009.”
Scientific knowledge on climate change and forecasting of the likely impacts has been advancing rapidly since the landmark 2007 IPCC report, and the UNEP compendium reviews some 400 major scientific contributions to our understanding of Earth Systems and climate change that have been released through peer-reviewed literature, or from research institutions, over the last three years.
Global growth in carbon dioxide emissions has exceeded even the most fossil-fuel intensive scenario developed by the IPCC at the end of the 1990s. Global emissions grew by 1.1 per cent each year from 1990–1999 and this accelerated to 3.5 per cent per year from 2000–2007.
The observed increases in greenhouse gas concentrations are raising concern that warming of between 1.4 and 4.3 degrees above pre-industrial surface temperatures could occur. This exceeds the range of 1–3 degrees perceived as the threshold for many “tipping points”, including the end of summer Arctic sea ice, and the eventual melting of Himalayan glaciers and the Greenland ice sheet.
Recent estimates of the combined impact of melting land-ice and thermal expansion of the oceans suggest a plausible average sea level rise of between 0.8 and 2.0 metres above the 1990 level by 2100. This compares with a projected rise of between 18 and 59 centimetres in the last IPCC report, which did not include an estimate of large-scale changes in ice-melt rates, due to lack of consensus.
“The science has become more irrevocable than ever. Climate change is happening. The evidence is all around us. And unless we act, we will see catastrophic consequences including rising sea-levels, droughts and famine, and the loss of up to a third of the world’s plant and animal species,” writes UN Secretary-General Ban Ki-moon.
According to the scientists, it may still be possible to avoid the most catastrophic impacts of climate change, but this will only happen if there is immediate, cohesive and decisive action to both cut emissions and assist vulnerable countries to adapt.
To download the full report, visit www.unep.org/compendium2009.