The hotter temperatures that the world is now experiencing (see The heat is on!) have a significant impact on weather generally.
Changing patterns and extremes
The two most important impacts of rising temperatures are:
- Weather patterns are changing. For example, some places will experience more rain than they used to, others less, and the annual weather patterns won’t always remain the same.
- We are likely to experience more extreme weather. The (Intergovernmental Panel on Climate Change warns of more severe storms, floods, droughts, heatwaves and cyclones.
Some people point to years (like Australia is currently experiencing) where the predicted effects of climate change (for example lower rainfall in southeastern Australia) are not occurring, and say this is evidence that our climate isn’t changing. But this is generally a misunderstanding. Greater weather variability and more frequent extremes of both wet and dry are part of climate change.
Observed impacts on weather
Ocean levels have risen globally by about 10 cm in the past 50 years. This is increasing the impacts of storm waves and coastal erosion.
Snow and ice melt
- Arctic sea ice has declined in extent by 10-15 per cent and its average thickness has decreased by 40 per cent over the last half century, and the rate of loss more than doubled in the last decade. The extent of the Arctic ice has impacts on other aspects of climate..
- Glaciers are in decline.
- Snow depth at the start of October (in Spring) has declined 40 per cent in the last 40 years in the Australian Alps.
Rainfall will become more variable and extreme – less rain in some locations but more in others, longer droughts, larger storm runoff over shorter periods of time and fewer years of “normal” rainfall and river flows.
For example the Australian Bureau of Meteorology has shown that part so the arid Australian inland are now receiving significantly more rain than they did 50 years ago (though this isn’t saying much as it was previously very dry), increasing in some places by 50mm each decade. Meanwhile, the productive farmland and major cities of the southeast are now receiving significantly less rainfall, decreasing at about 50mm per decade in some locations – and it will only get worse.
North Africa, already dry for the most part, is one location where further reduced rainfall is predicted.
Is there any doubt?
The scientists are convinced, because the data is there. The insurance industry is taking it seriously. It is happening, and it’s mostly bad.