3.7 Extreme weather

Global warming entails more intense precipitation, more and longer heat waves and fewer extremely cold days and nights. In many regions we can observe increasing summer dryness.  Severe droughts entail extreme wildfires, which in turn release huge amounts of carbon stored in forest grounds.

Long and severe droughts are in many cases interrupted by extreme precipitation and floods.  Flood damage has increased substantially the last decades

The physics behind is fairly easy: a warmer global climate means a warmer troposphere. A warmer troposphere means more evaporation from land and sea. The warmer air can hold more water vapor before it condenses to rain.

Warmer troposphere and oceans in polar regions lead to more icebergs floating around but also polar sea ice cover melting combined with more precipitation usually in the form of snow; and more open seas for longer periods. This disturbs cloud patterns, jetstreams and the polar vortex with its circumpolar winds, in turn impacting on weather patterns in the temperate and polar zones.

Low-lying coastal zones are particularly vulnerable through sea-level rise and changes in wave climate and stronger storms.

Studies suggest higher precipitation intensity for Northern Europe and increased dry-spell lengths for Southern Europe. High intensity and extreme precipitation are expected to become more frequent within the next 70 years. (Norwegian Meteorological Institute (2013) Extreme Weather Events in Europe: preparing for climate change adaptation)

flom

More precipitation

snow

Global warming means more periods of heavy snow in the Temperate and Arctic zones. A trend of more snow – more precipitation – is a warming indicator. Photo: Å. Bjørke

It is important to remember that global warming means more evaporation from the oceans to the air. More moisture in the air means more precipitation. As long as the temperature remains below 0 ° C, this precipitation will be coming as snow. In North Western Europe and the North East of the USA, this means global warming causes more rain and more heavy, wet, potentially very damaging snowfalls,  but gradually shorter winters.

Periods of heavy snow must be expected in the Nordic countries and parts of North America for several years ahead. The winter periods will become more erratic, with unusual mild periods in between cold periods. There will be more warm records than cold records. More icy roads for longer periods are likely.

Munich re: NAT CATS 2014: What’s going on with the weather?

Does global warming mean more or less snow?

American Meteorological Society (2016) Explaining Extreme Events from a Climate Perspective

Norge fra 1900 til i dag -Vær og klima i Norge har variert stort i gjennom historien

Making sense of future climate (CICERO, Jan 2017)

Drastic cooling in North Atlantic beyond worst fears, scientists warn (Feb 2017)

Events

Heatwaves, droughts and wildfires

Floods

Desertification

Storms

 

Insurance

 

 

NASA: Quiz weather extremes

Next

Home Chapter 3 3. Impacts
3.1 More water vapor
3.2 Sea level rise
3.3 Polar sea ice
3.4 Air pollution
3.5 Acidification
3.6 Health
3.7 Extreme weather
3.8 Economy
3.9 Refugees and conflicts
3.10 Glaciers
3.11 Tipping points
3.12 Biodiversity
3.13 Water
Chapter 4 4. Ecosystems