On a thermometer, a tenth of a degree seems tiny, barely noticeable. But small changes in average temperature can reverberate in a global climate to turn into big disasters as weather gets wilder and more extreme in a warmer world.
In 2015, countries around the world agreed to cut greenhouse gas emissions to limit global warming to 鈥渨ell below鈥� 2 degrees Celsius (3.6 degrees Fahrenheit) and pursue a goal of (2.7 Fahrenheit) as part of the Paris Agreement.
Two degrees of difference might not be noticeable if you're gauging the weather outside, but for global average temperatures, these small numbers make a big difference.
鈥淓very tenth of a degree matters,鈥� is a phrase that climate scientists around the world keep repeating.
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EDITOR鈥橲 NOTE: This story is part of an ongoing series answering some of the most fundamental questions around climate change, the science behind it, the effects of a warming planet and how the world is addressing it.
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The Earth has already warmed at least 1.1 degrees Celsius (2 degrees Fahrenheit) since pre-industrial times, giving the world around 0.4 degrees Celsius (0.7 Fahrenheit) of more heating before passing the goal and suffering even more catastrophic climate change events, .
These tenths of a degree are a big deal because the temperatures represent a global average of warming. Some parts of the world, especially land mass and northern latitudes have already warmed more than the 1.1 Celsius average and have far surpassed 1.5 Celsius, according to estimates.
It's helpful to look at temperatures like a bell curve, rather than just the average which doesn't reveal 鈥渉idden extremes,鈥� said Princeton University climate scientist Gabe Vecchi.
鈥淥n the far end where the bell shape is very narrow, that is telling you the odds of very extreme events,鈥� he said. 鈥淚f you have a slight shift of the average of the peak of that bell to the warming direction, what that results in is a substantial decrease in the odds of extremely cold temperatures and a substantial increase in the odds of extremely warm temperatures.鈥�
It's a similar picture with sea level rise, where the average obscures how some places are seeing much higher sea level increases than others, he said.
Most nations 鈥� including the world鈥檚 two largest emitters, the U.S. and China 鈥� aren鈥檛 on track to limit warming to 1.5 Celsius or even 2 Celsius, , despite promises to cut their emissions to 鈥渘et zero鈥�.
If temperatures increase by about 2 more degrees Celsius by the end of the century, the world will experience , according to estimates by the Intergovernmental Panel on Climate Change.
鈥淎ll bets are off鈥� when it comes to how climate systems will respond to more warming, warned Brown University climate scientist Kim Cobb. The threat of some and feedback loops that amplify warming, such as the that traps massive amounts of greenhouse gas, could trigger even more heating.
鈥淚t鈥檚 just staggering to think about how many people will be under immediate threat of climate-related extremes in a two degree world," Cobb said.
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Seth Borenstein And Dana Beltaji, The Associated Press
