Major new climate study rules out less severe global warming scenarios

Major new climate study rules out less severe global warming scenarios The study found the planet is most likely to warm 4.1 to 8.1 degrees if carbon dioxide doubles from preindustrial levels. Washington Post

The current pace of human-caused carbon emissions is increasingly likely to trigger irreversible damage to the planet, according to a comprehensive international study released Wednesday. Researchers studying one of the most important and vexing topics in climate science — how sensitive the Earth’s climate is to a doubling of the amount of carbon dioxide in the atmosphere — found that warming is extremely unlikely to be on the low end of estimates.

These scientists now say it is likely that if human activities — such as burning oil, gas and coal along with deforestation — push carbon dioxide to such levels, the Earth’s global average temperature will most likely increase between 4.1 and 8.1 degrees Fahrenheit (2.3 and 4.5 degrees Celsius). The previous and long-standing estimated range of climate sensitivity, as first laid out in a 1979 report, was 2.7 to 8.1 degrees Fahrenheit (1.5 to 4.5 Celsius).

If the warming reaches the midpoint of this new range, it would be extremely damaging, said Kate Marvel, a physicist at NASA’s Goddard Institute of Space Studies and Columbia University, who called it the equivalent of a “five-alarm fire” for the planet.

The new range is narrower than previous studies but shows at least a 95 percent chance that a doubling of carbon dioxide, which the world is on course to reach within the next five decades or so, would result in warming greater than 3.6 degrees Fahrenheit (2 degrees Celsius) relative to preindustrial temperatures. That is the threshold beyond which scientists say the Earth will suffer dangerous effects — disruptive sea level rise, intolerable heat waves and other extreme weather and permanent damage to ecosystems.

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Staying below that is still possible. If steep emissions cuts are made in the near-term, a doubling of carbon dioxide levels could be avoided. But if a doubling does occur, there would be a 6 to 18 percent chance of exceeding the upper bound defined by the study of 8.1 Fahrenheit (4.5 Celsius).