The Dirty Weather report

Published Wednesday, November 14, 2012 in the New Brunswick Telegraph Journal.

“What’s with all the dirty weather?” you may be wondering, in the destructive wake of Hurricane Sandy, and after yet another extreme rainstorm pounded NB last month. 

You’re right to wonder.  Extreme weather events like floods and droughts are ominous symptoms of climate change.  Here’s why.

A refresher from physics class
As our planet warms, our water cycle – the continuous movement of water up into the air as vapour and down again as rain or snow – is affected in several ways.

First, oceans and lakes are getting warmer, and water that’s warmer evaporates more easily.  Anyone who owns a swimming pool knows that more water evaporates from the pool surface on hot days than on cold days.

Secondly, air is getting warmer, and warm air can hold more moisture than cool air.  It’s a principle of physics, and it’s not a linear, one-for-one arrangement either: for every degree Celsius that air warms, its water holding capacity actually increases by 7%.  So that means warm air can hold and transport much more moisture than cold air can.  It’s estimated that the air over our oceans today is carrying 4% more water vapour that it was just 30 years ago.

Combine the above two phenomena and here’s what happens: oceans and lakes evaporate moisture more readily into the atmosphere; the warmer atmosphere absorbs a much bigger load of that moisture; and that moisture ends up falling in the form of extreme rainfall events. 

Hurricane Sandy is just the latest in a long string of weird weather events.  On October 20, over 80 mm rain (more than three inches) fell in Fredericton.  On September 9-10, much of Nova Scotia was deluged by over 100 mm rain; Truro was hit with severe flash flooding.  On September 5, Nappan, NS received 118 mm; NB’s Fundy coast received 108 mm.  Sure, fall rains happen – but three, four, even nearly five inches in a single event??

Flooding brings soaked basements, highway washouts and other costly fixes, all of which have to be paid for somehow.  No wonder insurance companies are among those most concerned about climate change.  In a study released last month, reinsurance giant Munich Re reports “a nearly quintupled number of weather-related loss events in North America for the past three decades”.  (I’m guessing Hurricane Sandy will prompt some rewriting; early numbers suggest repairs in New York alone will cost over $30 billion.)

Worse, governments and insurance companies are waking up to the uneasy reality that roads, storm sewers and other infrastructure built to yesterday’s standards may not be up to withstanding the rigours of a new climate reality.  After last month’s rainstorm in Fredericton, the lead headline in my local paper was “Infrastructure review called for in wake of weekend flooding”.  Again, read dollar signs.

More water, less water
Ironically, climate change causes more droughts too, because the same principle that causes water to evaporate faster from warmer oceans causes it to evaporate faster from warmer land too.  That means soils dry out quicker.  Also, snowpacks are expected to be smaller and melt earlier, creating problems for regions that depend on that meltwater.  NB’s snowpack has decreased by 25-50% over the last 30 years.

Droughts cause crop failures, with implications for farmers, food supplies and food prices.  Last summer’s US drought reduced corn production by 30%.  Rainfall pattern forecasts suggest that Mexico, the US and much of Europe are in the crosshairs to experience prolonged, severe drought by the end of this century.

24 Hours of Reality
If you’d like to learn more about the link between climate change and extreme weather, tune in to “24 Hours of Reality: The Dirty Weather Report”.  It’s a 24 hour climate awareness event to be livestreamed on the internet November 14-15 at  It will feature interviews with climate scientists and extreme weather stories from around the world, including our region.

Adapt, but prevent too
Today’s increased weather extremes underline the need for us to adapt to a new climate reality.  But adaptation alone doesn’t get to the root of the problem, which is our global addiction to fossil fuels.  The sooner we focus on transitioning away from oil, coal and natural gas, the less adapting our kids and grandkids will need to do.