Mediterranean rainfall immediately affected by greenhouse gas changes

February 17, 2020

Mediterranean-type climates face immediate drops in rainfall when greenhouse gases rise, but this could be interrupted quickly if emissions are cut.

This is the finding of new research published today in Proceedings of the National Academy of Sciences, which adds to the list of known benefits of rapidly reducing greenhouse gas emissions to keep global heating below 1.5°C.

Decreases in rainfall can impact the water resources of Mediterranean climates, which rely on winter rainfall to supply them through hot, dry summers.

The study, led by the University of Reading in collaboration with the National Research Council of Italy (CNR-ISAC, Bologna) and Imperial College London, reveals new ways in which climate change affects regions characterised by such climates, such as California, central Chile, and the Mediterranean region itself.

Previous modelling and observational studies have shown that most Mediterranean climates tend to become less rainy as the planet warms, with the exception of California. Mediterranean climates, which are characterised by hot and dry summers, are known to be particularly sensitive to decreases in wintertime rainfall. As a result, they are often described as 'hot spots' of climate change.

However, little was known about how the rate of greenhouse gas concentration increases affects these Mediterranean climates.

Lead author Dr Giuseppe Zappa, now at CNR-ISAC, said: "Whenever greenhouse gases are emitted, they immediately begin impacting climate, but the impacts develop over several timescales." Greenhouse gas build-ups in the atmosphere can affect local climates immediately - on the scale of just a few years - or gradually develop a significant impact over decades or even centuries, like sea-level rise.

Now, the team's modelling simulations of Mediterranean climates show that decreasing rainfall in the Mediterranean and in central Chile occurs rapidly alongside greenhouse gas rises, on the order of a few years.

According to Dr Paulo Ceppi, from the Grantham institute - Climate Change and Environment at Imperial: "Our result implies that water resources in these regions would almost immediately benefit from stabilising greenhouse gas concentrations, since this would interrupt the rapid decrease in rainfall. In other words, climate action is positive not only in the long term, but also after just a few years."

While California did not see the same rapid decrease in rainfall, the simulations showed in the long-term the region would still benefit from a steady increase in rainfall with stabilised emissions.

Although California is defined as a 'Mediterranean' climate, the team say the reason that it responds in a different way to warming than the actual Mediterranean and Chile lies in the ocean.

Dr Ceppi explains: "The warming of the ocean surface is not uniform, with some regions warming faster than others. The resulting ocean warming pattern affects winds and rainfall globally.

"Those areas of the ocean that warm faster than average cause remote changes in atmospheric winds that make Mediterranean regions drier. By contrast, other ocean areas that warm more slowly tend to make California wetter, while having little impact on rainfall in other Mediterranean regions."
-end-


Imperial College London

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.