The IPCC is the leading international body for the assessment of climate change. It was established in 1988 to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts.
The IPCC is a scientific body under the auspices of the UN. It reviews and assesses the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It does not conduct any research nor does it monitor climate- related data or parameters.
Scientists from all over the world contribute to the work of the IPCC on a voluntary basis. Review is an essential part of the IPCC process, to ensure an objective and complete assessment of current information. The IPCC is an intergovernmental body, open to all member countries of the UN and World Meteorological Organisation (WMO).
The IPCC produces comprehensive assessment reports on climate change every six years or so. The IPCC completed its Fifth Assessment Report (AR5) with the release of its Synthesis Report in late 2014. Over 830 scientists from over 80 countries were selected to form the author teams producing the report. They in turn drew on the work of over 1,000 contributing authors and over 1,000 expert reviewers. AR5 assessed over 30,000 scientific papers.
Besides the Synthesis Report, AR5 includes the contributions of IPCC Working Group I (the physical science basis of climate change), of Working Group II (impacts, adaptation and vulnerability) and of Working Group III (mitigation of climate change).
AR5 is the most comprehensive assessment of climate change ever undertaken and represents the best evidence available to inform the negotiations at COP21 with respect to the current state of the Earth’s climate system and its future trends. AR5 concluded that:
– Human influence on the climate system is clear and recent anthropogenic emissions of greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems.
– Warming of the climate system is unequivocal and, since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished and sea level has risen.
– Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century.
– Surface temperature is projected to rise over the 21st century under all assessed emission scenarios. It is very likely that heat waves will occur more often and last longer and that extreme precipitation events will become more intense and frequent in many regions. The ocean will continue to warm and acidify and global mean sea level will continue to rise.
Figure 2: Annually and globally averaged combined land and ocean surface temperature anomalies relative to the average over the period 1986–2005. Colours indicate different data sets.
Source: IPCC AR5 Figure SPM.1
Figure 3: Atmospheric concentrations of the greenhouse gases carbon dioxide (CO2, green), methane (CH4, orange) and nitrous oxide (N2O, red) determined from ice core data (dots) and from direct atmospheric measurements (lines)
Source: IPCC AR5 Figure SPM.1
Figure 4: Past and future sea-level rise. For the past, proxy data are shown in light purple and tide gauge data in blue. For the future, the IPCC projections for very high emissions (red, RCP8.5 scenario) and very low emissions (blue, RCP2.6 scenario) are shown.
Source: IPCC AR5 Fig. 13.27
Figure 1: Facts and figures around IPCC’s AR5 and the road to the COP21 negotiations
Source: Carbon Brief (www.carbonbrief.org)
– Many aspects of climate change and associated impacts will continue for centuries, even if anthropogenic emissions of greenhouse gases are stopped. The risks of abrupt or irreversible changes increase as the magnitude of the warming increases.
– Adaptation and mitigation are complementary strategies for reducing and managing the risks of climate change. Substantial emissions reductions over the next few decades can reduce climate risks in the 21st century and beyond, increase prospects for effective adaptation, reduce the costs and challenges of mitigation in the longer term and contribute to climate-resilient pathways for sustainable development.
These key findings are from the Summary for Policy Makers of the IPCC 2014 Synthesis Report.
The AR5 Synthesis Report tells a concise story, drawing on all three reports. It says that if governments work to cut emissions and adapt to new conditions, we can still keep the risks of climate change low. Nations have collectively agreed that beyond two degrees of warming, the risks posed by climate change are too high and it is unlikely we could deal with the consequences.
The IPCC concludes that, with the right policies, we can prevent dangerous climate change, allow ecosystems to adapt and ensure countries can develop sustainably, all at the same time.
On the other hand, the slower we take action, the harder it will be and the more expensive it will get. Not acting now puts a very heavy burden on future generations, the report says. It makes it clear that climate change is a collective problem. Because climate change affects everyone, nations must cooperate to limit it. It will only be possible to limit the extent of climate change if nations work together. As the UN Secretary-General has noted in relation to action to reduce climate change, “this is the planet where subsequent generations will live, and there is no Plan B, because we do not have Planet B”.
The IPCC is an advisory body – it does not tell the world’s leaders what to do. AR5 provides the best available scientific evidence and guidance for the negotiators at COP21 regarding the observed trends in climate changes and their predicted future paths, depending on the mitigation efforts that are achieved around emissions reduction. AR5 represents the clearest guide yet from scientists about why we need to keep climate risks in check. It concludes that human influence on the climate system is clear and that the more we disrupt our climate, the more we risk severe, pervasive and irreversible impacts.
The globally averaged temperature over land and ocean surfaces for 2014 was the highest among all years since recordkeeping began in 1880. We still have, however, the means to limit climate change and build a more prosperous, sustainable future. COP21 aims to finalise a new global agreement to limit greenhouse gas emissions and to help countries develop low-carbon and climate-resilient economies.
Figure 5: 2014 was the warmest year on record, with global temperatures 0.68°C above the long-term average. 14 of the 15 warmest years on record have occurred since the turn of the century.