Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond.
Projections of greenhouse gas emissions vary over a wide range, depending on both socio-economic development and climate policy. …
Continued emission 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 reductions in greenhouse gas emissions which, together with adaptation, can limit climate change risks.
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.
Warming caused by CO2 emissions is effectively irreversible over multi-century timescales unless measures are taken to remove CO2 from the atmosphere. …
[Limiting] total human-induced warming … to less than 2°C relative to the period 1861-1880 with a probability of >66% would require total CO2 emissions from all anthropogenic sources since 1870 to be limited to about 2,900 GtCO2 …
About 1,900 … GtCO2 were emitted by 2011, leaving about 1,000 GtCO2 to be consistent with this temperature goal.
Estimated total fossil carbon reserves exceed this remaining amount by a factor of 4 to 7 …
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.
Increasing magnitudes of warming increase the likelihood of severe, pervasive, and irreversible impacts for people, species and ecosystems.
Continued high emissions would lead to mostly negative impacts for biodiversity, ecosystem services, and economic development and amplify risks for livelihoods and for food and human security.
Many aspects of climate change and its 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.
Key drivers of future climate and the basis on which projections are made
Projected changes in the climate system
Future risks and impacts caused by a changing climate
Climate change beyond 2100, irreversibility and abrupt changes