Researchers say that the world has seriously underestimated the amount of heat soaked up by our oceans over the past 25 years, meaning the earth is more sensitive to fossil fuel emissions than estimated. This could make it much more difficult to keep global warming within safe levels this century, which has implications for sea level and for marine ecosystems
What have the researchers found?
The new study, reported in Nature, suggests that the seas have absorbed 60% more than previously thought. But it also means that far more heat than we thought has been generated by the warming gases we have emitted.
Therefore more heat from the same amount of gas means the Earth is more sensitive to CO2.
What are the implications of the finding?
The researchers involved in the study believe the new finding will make it much harder to keep within the temperature rise targets set by governments in the Paris agreement.
The report suggests that to prevent temperatures rising above 2C, carbon emissions from human activities must be reduced by 25% more than previously estimated.
What does it mean for the oceans?
As well as potentially making it more difficult to keep warming below 1.5 or even 2C this century, all that extra heat going into the oceans will prompt some significant changes in the waters.
“A warmer ocean will hold less oxygen, and that has implications for marine ecosystems,” said Dr Resplandy.
“There is also sea level, if you warm the ocean more you will have more thermal expansion and therefore more sea level rise.”
Will the heat ever come back out?
“The heat stored in the ocean will eventually come back out if we start cooling the atmosphere by reducing the greenhouse effect,” said Dr Resplandy.
“The ocean circulation that controls the ocean heat uptake/release operates on time scales of centuries, meaning that ocean heat would be released for the centuries to come.”
How have other scientists responded to the findings?
With some concern.
“The authors have a very strong track record and very solid reputation… which lends the story credibility,” said Prof Sybren Drijfhout at the UK’s National Oceanography Centre in Southampton.
Others say that further work is required.
“The conclusion about a potential higher climate sensitivity and potentially less allowable carbon emission to stay below 2C should stimulate further investigation.”