The UN-appointed Intergovernmental Panel on Climate Change published a new report Monday summarizing the latest authoritative scientific information about global warming. Here are five important takeaways.
The report says almost all of the warming that has occurred since pre-industrial times was caused by the release of heat-trapping gases such as carbon dioxide and methane. Much of that is the result of humans burning fossil fuels — coal, oil, wood and natural gas.
Scientists say that only a fraction of the temperature rise recorded since the 19th century can have come from natural forces.
Almost all countries have signed up to the 2015 Paris climate accord that aims to limit global warming to 2 degrees Celsius (3.6 Fahrenheit) — and ideally no more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) — by the year 2100, compared to the late 19th century.
The report's 200-plus authors looked at five scenarios and concluded that all will see the world cross the 1.5-degree threshold in the 2030s — sooner than in previous predictions. Three of those scenarios will also see temperatures rise 2 degrees Celsius above the pre-industrial average.
The 3,000-plus-page report concludes that ice melt and sea level rise are already accelerating. Wild weather events — from storms to heat waves — are also expected to worsen and become more frequent.
Because further warming is “locked in" due to the greenhouse gases humans have already released into the atmosphere. That means even if emissions are drastically cut, some changes will be “irreversible" for centuries, the report said.
While many of the report's predictions paint a grim picture of humans' impact on the planet and the consequences that will have going forward, the IPCC also found that so-called tipping points, like catastrophic ice sheet collapses and the abrupt slowdown of ocean currents, are “low likelihood,” though they cannot be ruled out.
The panel is composed of independent experts put forward by governments and organizations to provide the best possible scientific consensus on climate change.
Scores of scientists provide regular reports on a range of aspects of global warming that governments draw on when discussing what countries can contribute to curb greenhouse gas emissions and adapt to the impacts of climate change.