Climate: 1.5 degrees of warming nearly certain over land

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How hot will it be in 2100?

Stored ocean heat will be released for centuries to come

Staff Report

Warming of at least 1.5 degrees Celsius over most of Earth’s land areas is probably already locked into the climate system — even if greenhouse gas concentrations were capped at today’s levels.

The new climate change warning came from UK scientists who, in a new study, differentiated between the warming over land areas and the average global temperature increases often used in discussions about efforts to limit emissions of CO2 and other greenhouse gases.

The study was done by researchers with the UK Centre for Ecology & Hydrology and the University of Exeter and published in the journal Scientific Reports.

“It would certainly be inappropriate to create any additional fear over climate change. However, what this paper does is re-iterate that the oceans are currently acting as a very strong sink of heat,” said lead author Dr. Chris Huntingford from the Centre for Ecology & Hydrology. “Even if carbon dioxide was somehow stabilised at current levels, additional warming will occur as we move towards an equilibrium climate state.”

The scientists said their findings have implications for urban development, agriculture and natural systems like forests.

In a press release, the researchers described the two main reasons behind the result. Even if CO2 concentrations were to be capped at the current level, the
planet would continue to warm toward a new equilibrium at a higher temperature. At present, the climate is out of equilibrium, with the oceans drawing down very large amounts of heat from the atmosphere. However this will decline as the planet is bought towards a stable climatic state.

Second, warming rates over land are far higher than those when averaged globally which include temperatures over the oceans. This is a feature observed in meteorological measurements and reproduced across a large suite of climate models.

“Our findings suggest that we are committed to land temperatures in excess of 1.5 degrees Celsius across many regions at present-day levels of greenhouses gases,” said co-author Dr Lina Mercado, senior lecturer in physical geography at the University of Exeter. “It is therefore imperative to understand its consequences for our health, infrastructure and ecosystem services upon which we all rely.”

“Central to our methodology is analysis of predictions made by a large number of independent climate research centres from around the world,” Huntingford added. “Although many simulations exist for climate stabilization, these tend to be at future higher greenhouse gas concentrations. We were able to scale these back to see the warming levels we are already committed to, even if present-day concentrations increased no further.

“Such computer models capture how the ocean heat sink would be slowly lost as a stable climate is approached, implying that temperatures would continue to increase temporarily even if greenhouse concentrations were fixed at current levels.”

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