There has been a rapid increase of co2 concentrations in the atmosphere over the past 250 years: from 280 parts per million (ppm) to 379 ppm. All greenhouse gases add up to the equivalent of 430 ppm of co2. That this increase has had a warming effect because of heat energy trapped in the atmosphere is clear when one compares the well known hockey-stick graph of emissions with corresponding global temperature change.
There is a direct correlation between co2 build-up and temperature increase. The Earth has warmed by 0.7c since around 1900; 11 of the last 12 years (1995-2006) have been the warmest since temperatures were measured (1850). The world saw nearly stable temperatures for around 1,000 years and then a sharp increase since 1800.
The fact that climate change is real, that it is happening and that its impacts are devastating millions is no longer news. In its fourth synthesis report, the Intergovernmental Panel on Climate Change ( ipcc) has told us that the "warming of the climate system is unequivocal as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level". Clearly, the science of climate change has to be accepted even if its politics is still contested.
The only question that remains open is whether current science is underestimating the urgency and impact of climate change. ipcc is seen as conservative and cautious. Because of the time lag between its reports, it is feared that what we know today may already be out of date. Its current assessment does not take into account dramatic recent evidence, including the shrinking of the Arctic ice cap, news that Greenland is losing its mass faster than anticipated, a surge in atmospheric concentration of co2 and an apparent slowing of the Earth's ability to absorb greenhouse gases.
Taken together, it could well be that the climate is reaching its 'tipping' point, which will further accelerate changes in the years to come.
As far as climate change is concerned, the world is running out of time and options. We now know that the global atmospheric concentration of co2 has increased from a pre-industrial level of 280 parts per million (ppm) to 379 ppm in 2005. We also know that if this increase continues at the current rate, global temperatures could increase by 5-7 c above pre-industrial times by 2100. Scientists warn this increase would be catastrophic, indeed unimaginable.
The question is what level of temperature increase the world will be able to take. There is no clear answer because the numbers are intensely political.
It is important to note that global temperature has increased as of now by around 1c over pre-industrial levels and another 0.7c increase is inevitable in the years to come because of greenhouse gas emissions already in the atmosphere.The approximately 1.5 c increase in temperature is inevitable, at the very least.
What then is the limit that needs to be set for the future?
The latest report of the Intergovernmental Panel on Climate Change (ipcc) --of 2007--concludes that the world needs to keep co2 concentrations in the range of 350-400 ppm and the total concentration of greenhouse gases in the range of 450-500 ppm to keep the global mean temperature increase between 2c and 2.4c.
This will help avoid the worst impacts of climate change. But there will still be huge impacts.
The 2c goal will be a challenge. It will require the world to reduce emissions by 50-85 per cent on 2000 levels by 2050. To do this it has to reinvent and transform its strategies of energy use. It cannot get out of this mess by taking soft options.
The urgency of the need for this change cannot be overemphasized because greenhouses gases--especially co2 --stay in the atmosphere for very long periods. Every tonne we emit will further increase temperatures for years to come. It is for this reason that ipcc has concluded that to achieve the 2c goal, emissions just cannot increase after 2015, at the latest--meaning, seven years from now emissions must plateau and then drastically reduce.
Seen in another way this means that the world has already run out of time and spent its budget--at least as far energy is concerned. The International Energy Agency (iea) in its 2007 World Energy Outlook has concluded that the 2c challenge will require energy-related co2 emissions to be reduced to 23 billion tonnes in 2030--which is 13 per cent lower than 2005 emission levels. In other words, we have to cut what we already emit, forget emitting more. What then does this mean for the developing world, where the energy use of millions of people is way below their requirements? Combating climate change keeping in mind their needs is the real challenge.