02 February 2007 - With the strongest warnings yet from the international scientific community on the threat of dangerous climate change just published, it's clearly time to match strengths of scientific warnings with determined action to reduce greenhouse gas emissions.

The latest report on the science of climate change from the Intergovernmental Panel on Climate Change (IPCC) meeting in Paris, concluded that continuing polluting business-as-usual practices is likely to increase global average temperatures between 1.1°C and 6.4° C above 1980-1999 levels by 2095, leading to more droughts, heatwaves, floods and stronger hurricanes, rapid melting of ice-sheets and rapidly rising sea levels.

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Stephanie Tunmore, Greenpeace climate campaigner who was at the meeting in Paris said, "The good news is our understanding of the climate system and our impact on it has improved immensely. The bad news is that the more we know, the more precarious the future looks. There's a clear message to Governments here, and the window for action is narrowing fast. If the last IPCC report was a wake up call, this one is a screaming siren."

The main findings of the IPCC report are summarised below. Further reports will follow this year on at the probable impacts of climate change, options for adapting to those impacts, and possible routes to reducing emissions of greenhouse gases.

What's a few degrees?

While temperature increases of a few degrees might not sound so dramatic it will have dramatic effects on our climate. That's why is vital that action is taken now to reduce emissions and keep warming below 2°C to prevent catastrophic climate impacts.

Fortunately there is a blueprint for how to do this - the energy (r)evolution. It shows how to halve global CO2 emissions by 2050, using existing technology and still providing affordable energy and economic growth. In short - a revolution in energy policy and an evolution in how we use energy.

We can have reliable renewable energy, and use energy more smartly to achieve the cuts in carbon emissions required to prevent dangerous climate change. Crucially this can be done while phasing out damaging and dangerous coal and nuclear energy.

As the science of climate change becomes ever more clear and alarming, public concern is increasing rapidly. One of the few things not matching the warning is the scale of real action from governments to reduce emissions. If this stark warning goes unheeded future generations, enduring a warmer world of our own making, will not look kindly on lack of action at the start of the 21st Century.

Summary of major findings of the IPCC report

Human impact on climate has now been attributed with a 90 percent confidence, higher than in earlier assessments, and has been found in all world regions.

An increase in the theoretical climate ‘sensitivity’, i.e., how the climate will respond to a doubling of greenhouse gases in the atmosphere compared to pre-industrial levels. Previously, the best estimate for warming in relation to GHG doubling was 2.5 degrees centigrade, and now that has increased to 3 degrees centigrade.

Broad confirmation that the range of warming expected by 2100 if emissions are not reduced is 1.1°C and 6.4°C by 2095 over 1980-1999 levels (1). The intensity of tropical storms is likely to increase, a finding that was not possible in the Third Assessment Report (TAR). Observed increases in intensity are highly correlated with increased sea surface temperature.

The Antarctic and Greenland ice sheets contributed a substantial amount (around 15 percent) to the observed increase in sea level over the 1993-2003 period. However, the models say that the Antarctic ice sheet should in fact be growing, due to increased precipitation, meaning that as yet the models cannot explain the increase in the discharge of ice especially from Antarctica, and don’t fully account for the rapid melting and discharge of ice from Greenland. So, while it’s known that sea-level rise will probably be greater, it is still difficult to quantify precisely by how much.

A warming of 1.9 to 4.6°C above pre-industrial levels, (well within the range expected for the 21st century) would lead to the virtual elimination of the Greenland Ice sheet, if that warming is sustained for thousand years or more. That would raise sea level by between 6 and 7 metres. The report also found that future temperatures projected over Greenland are comparable to those from a warm period 125, 000 years ago, when sea levels were 4-6 metres higher than they are today.