Experts may be underestimating speed of global warming, says scientist

Global warming and climate change are words that almost everyone knows about now. That we should take major steps to slow the trend is also known. But now a notable climate scientist has said that experts may be underestimating how fast global warming is taking place. James Hansen, a prominent climate scientist has said that the average temperature on Earth will rise by 2 degrees Celsius above pre-industrial levels by the year 2050.

This level of increase is more than what's estimated by groups such as the Intergovernmental Panel on Climate Change, or IPCC. The estimates by the IPCC are generally considered the gold standard for climate forecasts.

In his new study, Hansen has said that the revised prediction is due to earlier underestimations of the effect greenhouse gases have on the atmosphere as well as the effects of aerosols which mask some of the global warming.

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The effect of aerosols on the climate system is well known.

NASA has previously said, "If not for aerosol pollution, Earth would be even warmer than it already is".

USA Today quoted Hansen who said that greenhouse gases and air pollution are something the climate is "more sensitive" towards.

Why is a 2-degree rise problematic?

A "2-degree rise in global temperatures is considered a critical threshold above which dangerous and cascading effects of human-generated climate change will occur," says NASA.

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In their paper, Hansen and his co-authors have said that as the world moves towards the 2-degree threshold, the "impacts on people and nature will accelerate".

The study, as reported by USA Today, has used improved paleoclimate data to say that Earth's climate "is more sensitive than usually assumed" to carbon dioxide and aerosols.

The authors of the study say that much of the warming in the last century has been offset and balanced by human-made aerosols, which have cooling effects.

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However, aerosols in the atmosphere have declined since the year 2010 because of reduced air pollution in China as well as restrictions on aerosols from ships.

"This aerosol reduction is good for human health, as particulate air pollution kills several million people per year and adversely affects the health of many more people," Hansen said. "However, aerosol reduction is now beginning to unmask greenhouse gas warming that aerosol cooling hid."

He was quoted by USA Today.

(With inputs from agencies)