IPCC report: human influence 'dominant' cause of global warming
Human influence on the climate system is "clear" and has been the dominant cause of global warming since the mid-20th century, according to the new assessment by the Intergovernmental Panel on Climate Change (IPCC).
Unveiling the first part of its fifth assessment (AR5) on climate change today, the IPCC says human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes.
Prior to the latest assessment, scientists were 90% agreed that humans were behind global warming but following the research for the latest report, they are now 95% certain.
They have said that warming of the climate system is "unequivocal", and since the 1950s, many of the observed changes are unprecedented over decades to millennia.
The report warns that continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system.
The 200 plus contributors to the assessment have concluded that CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions.
Projections of climate change have been based on a new set of four scenarios of future greenhouse gas concentrations and aerosols, spanning a wide range of possible futures.
Under all four scenarios, global warming will continue and global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850.
Co-Chair of Working Group I, Thomas Stocker, said: "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".
"Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions," he added.
The report is set to incentivise Governments and businesses into taking action on climate change and reducing CO2 emissions.
Commenting on the report, the Secretary of State for Energy and Climate Change Edward Davey said: "The gases emitted now are accumulating in the atmosphere and so the solutions must be set in motion today. 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. This strengthens the case for international leaders to work for an ambitious, legally binding global agreement in 2015 to cut carbon emissions," he added.
Investors have also reacted to the reports findings, which could encourage stronger investment in the low carbon industry if Governments around the world heed the IPCC's calls.
The Institutional Investors Group on Climate Change, which represents over 80 of Europe's largest investors, worth €7.5tn (£6.3tn), chief executive Stephanie Pfeifer said: "The IPCC's report re-confirms the necessity of urgent action on climate change. Business as usual is not an option. Unchecked climate change will increase the frequency and severity of extreme weather events, harming societies and causing ever steeper economic losses.
"The substantial and sustained cut in greenhouse gas emissions called for by the IPCC to avert dangerous warming will only be achieved with determined leadership at a policy level. Transitioning to a low-carbon economy requires strong, long-term climate and energy policies which breed confidence and spur investment. At the moment, inconsistent and unreliable policy signals are deterring investors and hampering investment in low-carbon energy solutions.