The IPCC released two major reports on Sunday (2nd November), a report which summarises the key findings from the three working group reports which were issued earlier in the year (see earlier blog here), and a summary report on the main findings.
This is the strongest and most unequivocal statement of scientific certainty from the IPCC. Some of the key points are below.
Observed changes and their causes
Human influence on the climate system is clear and recent anthropogenic emissions on greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems.
Observed changes in the climate system
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 levels have risen.
Causes of climate change
Anthropogenic greenhouse 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 these of other anthropogenic drivers have been detected throughout the climate systems and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century.
Impacts of climate change
In recent decades changes in climate have caused impacts on natural and human systems on all continents and across the oceans. Impacts are due to observed climate change, irrespective of its cause, indicating the sensitivity of natural and human systems to changing climate.
Future Climate Changes, Risks and Impacts
Continued emissions of greenhouse gases will cause further warming and long lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems. Limiting climate change would require substantial and sustained reduction in GHG emissions, which together with adaptation can limit climate change risks.
Predicted change in the climate system
Surface temperature is predicted 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 oceans will continue to warm and acidify and global mean sea level to rise.
Future risks and impacts caused by a changing climate
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.
This includes species extinction, lower oxygen levels for marine organisms, increased vulnerability for coral reefs and polar ecosystems, and increased risk to coastal and low lying regions from sea level rise.
Food security – marine biodiversity will be reduced affecting fisheries production, and in tropical and temperate regions, wheat, rice and maize will be negatively impacted when temps rise higher than 2˚C (although some locations may benefit).
Temperature increases of 4˚C or more combined with increasing food demand will pose large risks to food security globally.
Rural areas are expected to experience major impacts on water availability and supply, food security, infrastructure and agricultural incomes including shifts in the production areas of food and non-food crops.
Climate Change beyond 2100, irreversibility and abrupt changes
Many aspects of climate change and associated impacts will continue for centuries even if anthropogenic emissions of GHG are stopped. The risk of abrupt or irreversible changes
increase as the magnitude of warming increases.
Future pathways for adaptation, mitigation and sustainable development
Substantial emissions reductions over the next few decades can reduce climate risks in the 21st century and beyond, increase prospects for effective adaptation, reduce costs
and challenges of mitigation in the longer term and contribute to climate resilient pathways for sustainable development.
Risk reduction through mitigation and adaptation
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 / very high risk of severe, widespread and irreversible impacts globally.
Mitigation in the near term and throughout the century can substantially reduce climate change impacts in latter decades of the 21st century and beyond.
Some risks from climate change are unavoidable even with mitigation and adaptation.
There are multiple mitigation pathways that are likely to limit warming to below 2˚C relative to pre- industrial level. These pathways would require substantial emissions reductions over the next few decades and near zero emission of carbon dioxide and other long lived GHGs by the end of the century. Implementing such reduction poses substantial technological, economic, social and institutional challenges which increase
with delays in additional mitigation and if key technologies aren’t available.
Adaptation and mitigation
Many adaptation and mitigation options can help address climate change but no single option is sufficient by itself. Effective implementation depends on policies and co-operation at all scales and can be enhanced through integrated responses that link adaptation and mitigation with other societal objectives.
Mitigation options are available in every sector.
Effective adaptation and mitigation responses will depend on policies and measures across multiple scales, international, regional, national and subnational.
So it all makes for quite scary reading. What stood out for me is that the message is very strong and clear in that we are facing severe widespread and irreversible impacts if we don’t start to reduce emissions and mitigate our actions.
Carbon Visuals, a London based company which aims to help people visualise what carbon emissions look like, has produced this great little animation on what carbon emissions currently look like, and helps us to appreciate the size of the challenge that we all face to reduce GHG emissions
and create a sustainable future. The video can be accessed here.
Source: IPCC Climate Change 2014 Synthesis Report