How climate change causes extreme weather

Here’s a graphic to help explain one of the most immediate and direct impacts of climate change: extreme weather events.

Water Cycle

Image: US Geological Survey

Earth’s water cycle is a critical component of our climate.  It operates continuously, and has three stages:

  • Evaporation: water goes up into our atmosphere, mainly through evaporation from the surface of oceans
  • Condensation: cooler temperatures high in our atmosphere cause evaporated water to condense into droplets of moisture
  • Precipitation: this moisture falls back to the Earth in the form of rain or snow

We humans are most conscious of the third, because it’s the one that affects us directly.

Most people understand that global warming has warmed our air – but over 90% of the extra heat so far from global warming has actually gone into our oceans and warmed the water – and here’s why that combination is a big concern:

  • It’s a basic principle of physics that warm water evaporates more readily. So when oceans warm, much more water evaporates from their surfaces into the atmosphere.
  • It’s another basic principle of physics that warm air can hold and carry much more moisture (seven per cent more for every one-degree rise in temperature)

The result: warmer air carrying more moisture can drop enormous amounts of precipitation, whether as rain or snow, over an area.  In other words, extreme weather events.  (Just last week, I heard a television meteorologist attribute the stretch of wet weather we’ve been experiencing in eastern Canada to warmer water in the Gulf of Mexico.)

So – if ever you’ve wondered how climate change and extreme weather are related, now you know: intensification of our global water cycle, pictured above.  Perhaps that’s worth printing, or even sharing!  (Missed the graphics shared in the past three editions of Green Ideas?  You can find them here.)

Where we are, where we need to go

I get that your fridge may becoming a bit crowded by now – but here’s a third graphic worth printing and contemplating: where global greenhouse gas emissions currently stand, and where they need to go.

GHG Emissions

A special report issued last October by the UN’s Intergovernmental Panel on Climate Change (IPCC) concluded that, if we are to limit global warming to 1.5°C, we need to:

  • Reduce emissions globally by 45% from 2010 levels by 2030 (just 11 years from now); and then
  • Achieve net zero emissions by 100% by 2050, just 20 years after that

The IPCC’s conclusion is represented by the dotted red line above.  (The solid red line represents continuing with ‘business as usual’.)

A few takeaways:

  • A 45% reduction in just 11 years is a daunting goal by any measure; it won’t be achieved if we fall into the trap of thinking we can wait 10 years and then just do it all in the 11th, so we need to act quickly
  • A 45% reduction is not just a minor tweak; it will require deep, fundamental changes to where we get our energy and how we use it
  • A 45% reduction for all translates into a 45% reduction for each of us, so here’s the big question: what can you (or I) do to reduce our carbon footprint by 45%? (To help, why not revisit this graphic of the sources of Canada’s greenhouse gas emissions by sector, from March 27’s Green Ideas.)

True, you or I can’t do it alone.  But it’ll never get done without us.