What's the single most important number in the new report from the Intergovernmental Panel on Climate Change? 2020.
Carbon pollution is heating up the planet, raising sea levels, melting sea ice and glaciers at an increasing pace, acidifying the oceans and increasing many regions' danger from heat waves, floods and damaging storms, according to the landmark scientific report released today.
This report contains plenty of facts and figures. IPCC's experts forecast catastrophic climate changes if the world continues on the current fossil fuel-intensive emissions pathway, including a global average temperature increase of up to 10 degrees Fahrenheit; global average sea-level rise maximums exceeding 3 feet; a more than 100 percent increase in ocean acidity by the end of the century; and near-complete loss of the Arctic's summer sea ice before mid-century.
But the single-most important number is clearly 2020 -- the latest year that carbon pollution must peak to avert catastrophic impacts from climate change.
The report, prepared by more than 800 of the world's leading experts, underscores the disturbing fact that pollution-control efforts by President Barack Obama and other world leaders fall far short of the greenhouse gas reductions needed to avert catastrophic climate change.
As a scientist, I can't imagine a clearer warning: Left unchecked, the climate crisis threatens people and wildlife around the globe.
It's clear from this report that warming is damaging our world -- and that many of the dangerous effects are happening faster than expected. Unless President Obama and other world leaders move much more swiftly to reduce emissions, climate change will fundamentally transform our planet.
According to the report, it is still possible to avoid the worst climate impacts if global governments instead adopt the IPCC's lowest emissions pathway, which requires global emissions to peak by 2020 at the latest (and the earlier the better), with substantial declines in emissions afterwards.
This pathway would lead to a 70 percent reduction in mean temperature rise, a 40 percent reduction in sea-level rise, and an 85 percent reduction in ocean acidity rise by 2100, as well as preserving summer sea ice, compared with our current pathway.
The Obama administration has begun rolling out policies intended to cut emissions, but these measures are too slight and come too late to head off catastrophic climate change. The administration's recently announced "New Source Performance Standards" for new power plants, for example, will make only minor cuts to power plant pollution over the coming years.
The power plant measure is aimed at fulfilling the Obama administration's pledge to put the United States on the path to cutting greenhouse gas emissions by 4 percent below 1990 levels by 2020. But such a reduction falls far short of what the U.S. pledged in the Kyoto Protocol and -- as the IPCC report makes clear -- would not be enough to avert catastrophic temperature increases, sea-level rise, droughts, floods and other climate disruption.
The Clean Air Act provides proven successful programs to achieve science-based greenhouse pollution reductions, which is why dozens of communities around the country have already joined the Clean Air Cities campaign by passing resolutions urging the Obama administration to implement the Clean Air Act for ambitious greenhouse pollution cuts.
In the wake of the IPCC report, the message from the world's scientists is loud and clear: Rapid, bold cuts in carbon pollution should be our first priority. We have a deadline. Now it's time to get to work.