Vast climate reanalysis holds extreme weather clues
An EU-funded project collected, digitalised and analysed huge amounts of climate data from 1900 to 2010, revealing climate change clues and building global models that could help anticipate extreme weather, potentially saving lives.
© Laure F #37043294, 2019 source: stock.adobe.com
Predicting climate change and increasingly dramatic and devastating weather events, as well as creating strategies to tackle these problems, requires a deep understanding of how the climate has evolved over the past century.
The EU-funded ERA-CLIM2 project helped to further deepen such insight by harvesting data on the atmosphere, land, ocean and sea ice spanning more than 100 years.
We rescued and reprocessed past conventional and satellite data and developed and applied new coupled ocean atmosphere data assimilation methods allowing for state-of-the-art climate reanalyses for the entire 20th century, says ERA-CLIM2 project coordinator Roberto Buizza, lead scientist at the European Centre for Medium-Range Weather Forecasts in the UK.
Reconstructing the climates past
ERA-CLIM2s data and methods could help climate scientists estimate when an extreme climatic event such as a wind storm, flood or heat wave, may reoccur by analysing the frequency and timing of these events in the past.
The project recovered previously unused climate observations from old, handwritten records found in national archives, shipping route reports and some old, local weather stations.
Millions of observations were rescued, digitalised and added to datasets as part of a long and painstaking task, says Buizza.
While older climate observations are much more limited before the arrival of satellite in the 1970s, and even more limited before the invention of radiosonde measurements in the 1930s, the project used the data it found to make simulations of ocean, land and atmosphere processes.
ERA-CLIM2 scientists also used old satellite data and reprocessed it with the latest software to improve its quality.
The project then generated a fresh analysis of the Earths past climate with variables such as temperature, wind, pressure, humidity, precipitation and cloud cover, as well as sea surface temperature, on a 3D mesh that covers the whole globe.
It is the first reanalysis of the Earths system that includes ocean currents, waves and salinity profiles, sea ice, land, atmosphere and carbon analysis over the 20th century. The mesh starts at the bottom of the ocean and goes 80 km up into the atmosphere.
Carbon budgets and climate extremes
ERA-CLIM2 researchers tracked the evolution of the global carbon budget emissions and sinks from 1870 to 2012. They found that, on average, half of the carbon dioxide from anthropogenic sources emitted by burning fossil fuels like coal and oil has remained in the atmosphere with the other half being captured by the land and oceans.
Project researchers were also able to understand why a past climatic event happened. In December 1916, during the First World War, massive snowfall in the Southern Alps triggered avalanches killing thousands of soldiers and civilians. By reanalysing data, they revealed the atmospheric conditions that led to it including moisture transport from the warm Mediterranean Sea towards the Alps and a dangerous rain on snow situation.
ERA-CLIM2 rescued past data, quality controlled it and prepared it to be used in future reanalyses to be carried out by the EUs Copernicus Climate Change Service. This includes 3D ocean, sea ice, land and atmosphere assimilations, as well as the development of a global registry to track similar data recovery efforts worldwide.
Coupled reanalyses such as the one produced by ERA-CLIM2 will become increasingly popular since they can provide a consistent view of the evolution of the Earths climate, says Buizza. And they can help us understand, for example, how atmospheric warming due to greenhouse gases changes throughout the years, linked to the role of the oceans in storing part of it.