This report, based on the reports of the three working groups of the Intergovernmental Panel on Climate Change (IPCC), was published on 1 November 2014. It provides an integrated view of climate change and is the final part of the IPCC’s Fifth Assessment Report.

The report is written in the cautious and carefully judged words of scientists who have studied the research in depth and who know that the world’s politicians are looking over their shoulder. The words of the report are clear, calm and authoritative.

On the evidence for global warming

‘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.’

The causes

‘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.’

The consequences

‘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 to rise.’

The risks

‘Climate change will amplify existing risks and create new risks for natural and human systems. Risks are unevenly distributed and are generally greater for disadvantaged people and communities in countries at all levels of development.’ ‘Without additional mitigation efforts beyond those in place today, and even with adaptation, warming by the end of the 21st century will lead to high to very high risk of severe, widespread, and irreversible impacts globally .’

The report calls for both much more work to mitigate risk of climate change by reducing our carbon emissions and by adapting to those impacts of climate change that are now very likely.

All quotes are from the ‘Approved Summary for Policymakers’, 1 November 2014. For more details and to download the report go to the IPCC website: http://www.ipcc.ch/

 

Adrian Shaw