Not Just CO2: These Climate Pollutants Also Must Be Cut to Keep Global Warming to 1.5°C

Countries won't be able to limit global warming to 1.5 degrees Celsius above pre-industrial levels, considered by some scientists and policymakers to be the "safe" limit of climate change, without immediate and rapid reductions in a wide range of greenhouse gases, not just carbon dioxide, according to a new United Nations report.

The report, released Oct. 8 by the Intergovernmental Panel on Climate Change, sums up the research into how 1.5°C of warming will affect the world and how global warming can most effectively be stopped.

The planet has already warmed about 1°C since the start of the industrial era, and that's likely to reach 1.5°C between 2030 and 2052 if emissions continue at their current rate, the IPCC says.  It describes how recent warming has been accompanied by a trend toward more intense and frequent climate, temperature and weather extremes, and how those risks will rise with the temperature.

The warming can be stopped, the IPCC writes in its summary for policymakers.  Doing so will require countries to reduce global net emissions of carbon dioxide to zero by around 2050 and to also significantly reduce short-lived climate pollutants, including methane, black carbon and hydrofluorocarbons, or HFCs.

That emphasis on reducing short-lived climate pollutants, which are many times more potent than CO2 but don't last as long in the atmosphere, is stronger than what has been written into past international agreements.

That's partly because, with the clock running out before the world busts through its carbon budget, curtailing short-lived pollutants can buy valuable time.

In analyzing the least disruptive pathways for keeping global warming under 1.5°C, the IPCC found that all involve deep reductions in both methane and black carbon emissions of at least 35 percent by 2050.

Read more at Not Just CO2:  These Climate Pollutants Also Must Be Cut to Keep Global Warming to 1.5°C