The ground-breaking 1990 report on climate change has been updated to include further warnings of the catastrophic effects of global warming
According to the new assessment by the Intergovernmental Panel on Climate Change (IPCC), it is ‘highly likely’ that humans have been the main cause of global warming over the last 20 years.
‘Observations of changes in the climate system are based on multiple lines of independent evidence. Our assessment of the science finds that the atmosphere and ocean have warmed, the amount of snow and ice has diminished, the global mean sea level has risen and the concentrations of greenhouse gases have increased,’ said Qin Dahe, co-chair of the IPCC working group.
With predicted continuing global warming, the report said the world would experience more sustained heat waves, with wet regions receiving more rainfall and dry areas becoming drier.
Thomas Stocker, the other co-chair of the working group added: ‘Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.
‘Heat waves are very likely to occur more frequently and last longer. As the Earth warms, we expect to see currently wet regions receiving more rainfall, and dry regions receiving less, although there will be exceptions.’
The last IPCC assessment took place in 2007. The important report consults more than 200 experts and includes the results of a number of major research programmes. It is considered to be the most comprehensive view on the state of the changing climate.
Key facts from the report
- Since the 1950s many of the changes taking place have been unprecedented
- Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850
- Over the last two decades, the Greenland and Antarctic ice sheets have shrunk and it is very likely that the Arctic sea ice cover will continue to shrink and thin during the 21st-century
- The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years
- CO2 concentrations have increased by 40 per cent since pre-industrial times
- Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system
- Changes in the global water cycle in response to the warming over the 21st century will not be uniform
Reaction to the report
William Hague, foreign secretary
‘The UN Intergovernmental Panel on Climate Change’s latest assessment of the science confirms that climate change is already happening, as a result of human activity. The odds of extreme weather events, which threaten lives and property, have increased. Sea levels are rising, and ice is melting faster than we expected.
‘The IPCC’s report makes clear that unless we act now to reduce carbon emissions, all this will continue to worsen in coming decades. Governments, businesses and individuals all have a responsibility to tackle climate change. The longer we delay, the higher the risks and the greater the costs to present and future generations.’
Robert Gibson, British high commissioner
‘The result of this latest report is a full and undeniable picture of climate change. As difficult as the headlines may be to accept, the science is clear for all. The thermometers don’t lie: global warming is unequivocal. And the report has strengthened the argument that climate change is manmade. Global temperatures have risen by 0.9°C since 1901. Global sea levels have risen 0.2m since 1901. The area covered by arctic sea ice cover in the summer has reduced by about 40 per cent since 1979. The Greenland and Antarctic ice sheets are losing mass, as are the majority of glaciers worldwide. There are increased weather extremes and in the coming decades the likelihood of increased risks from extreme events.
‘The latest evidence suggests that without urgent action to reduce greenhouse gas emissions, we will likely see at least a 2°C and potentially as much as a 5°C rise in global temperatures by the end of this century. There is no surprise then that the report concludes that to have just a two-thirds chance of meeting the UN’s 2°C target, we need to limit future greenhouse emissions’.
Paul King, chief executive, UK Green Building Council
‘The IPCC’s report provides unequivocal evidence that humans are the driving forcing behind climate change, and sends a clear message to policy makers that now is the time to act. The built environment offers by far the most cost–effective mitigation potential of any sector.
‘We must see greater urgency from politicians and the private sector to drive down carbon, and to capitalise on the business opportunities in doing so.’
David MacKay, chief scientific advisor to the Department of Energy and Climate Change
‘This latest report is the most authoritative and comprehensive report to date of our understanding of climate change. The scientific consensus is that the world has warmed and will warm more, owing to human activities. There is robust evidence that human greenhouse gas emissions are already changing our world; global temperatures have risen every decade for the last three decades, oceans are acidifying, rainfall patterns are changing, sea levels are rising, arctic sea ice is declining, and some extreme weather events are becoming more frequent and intense.
‘One important message of this new report is that, while there remains some uncertainty about the precise sensitivity of the climate to greenhouse gas emissions, the impact on climate is largely determined by the cumulative total of humanity’s carbon emissions. This means that waiting a decade or two before taking climate change action will certainly lead to greater harm than acting now.’
Wolfgang Feist, Passivhaus Institute
‘Science is now in the position to acknowledge the influence of human activities on the climate. The clarity of the facts presents an opportunity to prevent serious consequences.
‘There are many examples demonstrating how societies can draw the right conclusions on the basis of scientific facts: acid rain, ozone depletion, smoking. In retrospect, it often becomes clear how misguided resistance by interest groups is. Seen objectively, their actions frequently even damage their own causes.
‘There is no longer any scientifically founded doubt that the planet’s climate is changing due to rising CO2 emissions.’
Samantha Smith, leader of WWF’s Global Climate & Energy Initiative
‘There are few surprises in this report but the increase in the confidence around many observations just validates what we are seeing happening around us. Since the IPCC issued its last big report in 2007, terrestrial glacier loss and sea-level rise has dramatically accelerated; the Arctic summer sea ice losses are higher than originally projected and the last decade was the warmest since 1850.’
Andy Atkins, executive director, Friends of the Earth
‘Scientists are now as convinced that humans are causing climate disruption as they are that smoking causes cancer - politicians can’t continue to stand idly by while the world goes spinning towards climate catastrophe.
‘Tough action is urgently needed to end the planet’s dangerous fossil fuel fixation and to develop the huge job-creating potential of renewable power - with developed nations like Britain taking the lead.
‘The coalition government must seize the initiative, starting with a 2030 decarbonisation target for the power sector. Faced with overwhelming scientific evidence, supported by the public, there is no excuse for failing to act on climate change.’