Human influence on climate is clear, and urgent action is needed
The dust has settled from the launch of the fifth Intergovernmental Panel on Climate Change (IPCC) Working Group One report, Climate change 2013: the physical science basis, and the evidence pointing towards unprecedented climate change, and the anthropogenic element of this, is stronger than ever.
Climate changes over past few hundreds of years have been unprecedented, says the report, which states that ‘it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.’
The report states with at least 66% certainty that the last three decades have been the warmest in 1,400 years. Global temperatures have risen by 0.9°C in the last century, and the report lays bare the role of the oceans in storing a lot of this heat, an effect that could detrimentally affect marine life, and which will result in rising sea levels due to thermal expansion.
If emissions continue as they are, by 2050 there is likely to be a further temperature rise of 1.4–2.6°C, says the report. This could be reduced to 0.4–1.6°C, but only if emissions were halted almost immediately, and carbon dioxide was then actually extracted from the atmosphere. ‘Substantial and sustained’ cuts in carbon emissions need to be taken to limit the effect of heatwaves, melting ice and sea level rise, and extreme weather, it adds.
The report also highlights the dramatic loss of ice from ice sheets and sea ice, particularly in the northern hemisphere.
Some that doubt the science behind climate change had pointed to a disparity between carbon levels in the atmosphere and the level of warming seen over the last 15 years. The report explains this as natural variability in the climate system due to other factors affecting temperatures, such as solar activity, and repeats that the long-term climate trend is consistent.
AR5, as the report is known, is different to previous IPCC reports, in that it recommends a ‘carbon budget’ to stay below the well-quoted 2°C limit to avoid ‘dangerous’ climate change. In this section it states that around half of the maximum level of carbon dioxide that can be emitted to stay below this threshold has already entered the atmosphere.
There are still uncertainties, particularly around the ‘climate sensitivity’ – how the atmosphere will respond to a given amount of carbon dioxide entering it. The best guess for this has been lowered in AR5, but only by a small amount.
Following the release of the report, UK Secretary of State for Energy and Climate Change Edward Davey said: ‘The risks and costs of doing nothing today are so great, only a deeply irresponsible government would be so negligent… without urgent action to cut greenhouse gas emissions this warming will continue, with potentially dangerous impacts upon our societies and economy.’
Responding to sceptics of climate science, the EU’s Climate Action Commissioner Connie Hedegaard said: ‘The issue is not whether to believe in climate change or not. The issue is whether to follow science or not. The day when all scientists with 100% certainty warn you against climate change, it will be too late. If your doctor was 95% sure you had a serious disease, you would immediately start looking for the cure. Why should we take bigger risks when it's the health of our planet at stake?’
News Item details
Journal title: Energy World
Keywords: climate change - international cooperation - Climate Change - Government Policy
Countries: Worldwide -
Organisation: Department of Energy and Climate Change
Subjects: Sea-levels, Carbon emissions, Carbon dioxide
