Climate emergency – extreme weather events

Climate emergency – extreme weather events

It is hard for most people to envision how an additional 2°C of global heating might affect daily life – what’s wrong with a few nice summers?  Predicted sea-level rises happen over timescales so long that building better flood defences might be thought to be easy.

But the average change in the climate manifests itself in greater variability in weather and more extreme weather events. Heatwaves and fires, floods and storm surges, droughts and water contamination are causing greater loss and damage. Of course, many weather extremes are the result of natural climate variability (including phenomena such as El Niño). Even if there were no anthropogenic changes in climate, a wide variety of natural weather and climate extremes would still occur.

The IPCC say that globally, since 1950, the length or number of warm spells or heatwaves has increased there have been more heavy rains, though there are strong regional and subregional variations in the trends. There has been a trend to more intense and longer droughts in southern Europe and West Africa, though central North America and northwestern Australia the droughts have become less frequent, less intense, or shorter.

Looking forward the IPCC models suggest it is virtually certain there will be increases in the frequency and magnitude of warm daily temperature extremes and decreases in cold extremes. The length, frequency, and/or intensity of warm spells or heat waves will increase over most land areas. The frequency of heavy precipitation or the proportion of total rainfall from heavy rainfalls will increase in the 21st century over many areas of the globe.

The UN warned that we are now seeing one climate crisis disaster each week, and argued for greater and immediate in plans for adaptation, as well as reducing emissions.  New standards for infrastructure, such as housing, road and rail networks, power and water supply networks are needed to make them resilient to more extreme conditions.

A Pentagon report reveals that more than two-thirds of operationally critical military installations are threatened by the effects of climate change over the next 20 years. The main impacts came from recurrent flooding, drought, and wildfires.  Examples include increased flooding at the Langley Air Force Base, drought conditions at several DoD bases in Washington DC damaging infrastructure, and wildfire at Vandenberg Air Force Base in southern California affecting space launch complexes. They were also concerned about effects around the world – for example recurrent flooding at the Naval Base in Guam is limiting capacity for a number of operations and activities including submarine squadrons.

Wildfires. In Northern Europe, between 20 and 200 times more area burned than normal, with fires raging as far north as the Arctic circle. Climate change is estimated to have lengthened fire seasons across a quarter of the world’s vegetated land surface. In the Western U.S., large fires are now almost seven times more likely to occur than three decades ago, forest areas burned have doubled since 1984. Also, as the world urbanises, the interface between fire areas and habitation increases, with greater risk to life and property.  The fires of 2017 and 2018 cost the insurance industry more than $15 billion each year, forcing reinsurers to reconsider their view of wildfire losses and raising the prospect of large numbers of homes becoming uninsurable.  Wildfires in the Arctic are at “unprecedented levels” with areas of Siberia, Alaska, Greenland and Canada engulfed in flames and smoke, and strong winds have made this year’s fires particularly bad.

Heatwaves. This July’s heatwave in Europe has set records in 3 countries, and is linked with several deaths. There are also the effects of variability of temperature increase locally. Temperature rises in many major cities would far exceed the global average of 2°C. A recent study suggested that, instead of just 2°C, Madrid’s temperature would rise by 6.4°C, London by 5.9°C and New York’s by 4°C.  London could suffer from the type of extreme drought that hit Barcelona in 2008, when it was forced to import drinking water from France at a cost of £20 million.

Monsoons. Nearly half the world’s population live in areas affected by monsoons. In India around 75% of rainfall occurs in the monsoon season, making any variation in its behaviour critical for agriculture, livelihood and basic survival.  Monsoons are triggered by a contrast in temperature between land masses and oceans, which triggers a reversal of wind patterns, causing an increase in precipitation. As temperatures increase as a result of climate change, monsoons are altered, and levels of rainfall are skewed. Monsoons are becoming more unpredictable and irregular, entering periods of reduced rainfall in certain regions, specifically southern Asian regions, and is projected to worsen in the future. In 2018, rainfall increased, causing floods and landslides.

Floods. The IPCC noted in its special report on extremes, it is increasingly clear that climate change “has detectably influenced” several of the variables that contribute to floods, such as rainfall and snowmelt. In other words, while our warming world may not induce floods directly, it exacerbates many of the factors that do.

Storms/hurricanes. Researchers in North Carolina examined hurricanes Floyd, Matthew and Florence and found that the probability of them occurring randomly in such a short period of time is just two per cent. Six out of the seven largest hurricanes since 1898 occurred in the last 20 years. This frequency is probably caused by “increased moisture carrying capacity of tropical cyclones due to the warming climate”.

Attribution. Despite the evidence of an increase in extreme weather events on average, a problem that climate scientists have always faced is saying whether any specific event is caused by global heating, rather than just being a natural outlier. This has left room for doubt to be sown in the minds of the public. To address this “attribution science” is developing new approaches. Increasing computer power, combined with a massive increase in data points, has enabled more sophisticated simulation modelling that can begin to show the direct effects of climate change. Many studies have shown that climate change has increased the scale of a weather event – eg greater rainfall in Hurricane Harvey.   But some have begun to show that a weather event would not have happened at all were it not for global heating. The World Weather Attribution project  has made real and significant advances in isolating the climate signal in the costly impacts of extreme events, in both developed and developing countries.

 

Written by Huw Williams, SAMI Principal

Image by Gerd Altmann from Pixabay

The views expressed are those of the author and not necessarily of SAMI Consulting.

SAMI Consulting was founded in 1989 by Shell and St Andrews University. They have undertaken scenario planning projects for a wide range of UK and international organisations. Their core skill is providing the link between futures research and strategy.

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