But adaptation alone is not enough. Substantial and sustained reductions of greenhouse gas emissions are at the core of limiting the risks of climate change. And since mitigation reduces the rate as well as the magnitude of warming, it also increases the time available for adaptation to a particular level of climate change, potentially by several decades.
There are multiple mitigation pathways to achieve the substantial emissions reductions over the next few decades necessary to limit, with a greater than 66% chance, the warming to 2ºC – the goal set by governments. However, delaying additional mitigation to 2030 will substantially increase the technological, economic, social and institutional challenges associated with limiting the warming over the 21st century to below 2ºC relative to pre-industrial levels, the report finds.
“It is technically feasible to transition to a low carbon economy,” said Youba Sokona, Co-Chair of IPCC Working Group III. “But what are lacking are appropriate policies and institutions. The longer we wait to take action, the more it will cost to adapt and mitigate climate change.”
The Synthesis Report finds that mitigation cost estimates vary, but that global economic growth would not be strongly affected. In business-as-usual scenarios, consumption – a proxy for economic growth – grows by 1.6 to 3 percent per year over the 21st century. Ambitious mitigation would reduce this by about 0.06 percentage points. “Compared to the imminent risk of irreversible climate change impacts, the risks of mitigation are manageable” said Sokona.
These economic estimates of mitigation costs do not account for the benefits of reduced climate change, nor do they account for the numerous co-benefits associated with human health, livelihoods, and development.
“The scientific case for prioritizing action on climate change is clearer than ever,” Pachauri said. “We have little time before the window of opportunity to stay within 2ºC of warming closes. To keep a good chance of staying below 2ºC, and at manageable costs, our emissions should drop by 40 to 70 percent globally between 2010 and 2050, falling to zero or below by 2100. We have that opportunity, and the choice is in our hands.”
The Synthesis Report, written under the leadership of IPCC Chair R. K. Pachauri, forms the capstone of the IPCC Fifth Assessment Report. The first three volumes, based on outlines approved by the IPCC’s 195 member governments in October 2009, were released over the past fourteen months: Climate Change 2013: The Physical Science Basis in September 2013, Climate Change 2014: Impacts, Adaptation and Vulnerability in March 2014 and Climate Change 2014: Mitigation of Climate Change in April 2014.
IPCC reports draw on the many years of work by the scientific community investigating climate change. More than 830 coordinating lead authors, lead authors and review editors from over 80 countries and covering a range of scientific, technical and socio-economic views and expertise, produced the three working group contributions, supported by over 1000 contributing authors and drawing on the insights of over 2,000 expert reviewers in a process of repeated review and revision. The authors assessed more than 30,000 scientific papers to develop the Fifth Assessment Report. About 60 authors and editors drawn from the IPCC Bureau and from Working Group author teams have been involved in the writing of the Synthesis Report. Their work was made possible by the contributions and dedication of the Synthesis Report Technical Support Unit.
“I would like to thank the hundreds of experts from the world’s scientific community who have given freely of their time and expertise to produce the most comprehensive assessment of climate change yet undertaken,” said Pachauri. “I hope this report will serve the needs of the world’s governments and provide the scientific basis to negotiators as they work towards a new global climate agreement.”
Click here to read/download the full Climate Change 2014: Synthesis Report.