US climate assessment is grim

Hot on the heels of the IPCC’s dramatic October report on the climate impact of 1.5 degrees of global warming comes an even harder-hitting assessment from a prestigious US government program called the Global Change Research Program.  Weighing in at an impressive 1566 pages, there is thankfully a 175-page Report-in-Brief which still strongly conveys the core message that planet Earth is in serious trouble, and that it’s going to get a lot worse before it gets better—if it ever does, which is not at all certain the way things are going.


The US report is also an easy read—an accolade that the IPCC reports, steeped in caution and all hung about with disclaimers, caveats, and estimates of confidence levels and probabilities, have never managed too earn. So there is no excuse not to take a look and think about what can be done to try and slow down the rate at which we are pumping billions of tonnes of gas-phase carbon into the atmosphere every year and slowly overcooking the planet.

The Fourth National Climate Assessment (NCA4) is focused on the US, but greenhouse gases don’t wait at the Canadian border asking for permission to enter, and global warming is actually happening faster in the northern reaches of Canada than it is in more southerly regions. So the report has lots of information and warnings of relevance for Canadians.

But first, in case Donald Trump may finally be paying attention (although no signs of that so far), NCA4 states once again and for the record:

Observations collected around the world provide significant, clear, and compelling evidence that global average temperature is much higher, and is rising more rapidly, than anything modern civilization has experienced, with widespread and growing impacts. The warming trend observed over the past century can only be explained by the effects that human activities, especially emissions of greenhouse gases, have had on the climate.

Variations in solar output and other geophysical phenomena have only a small impact on global warming.  This has been confirmed by numerous peer-reviewed and definitive scientific studies.

NCA4 has 12 summary findings, but after an introductory warning about the risks to human health and safety, quality of life, and the rate economic growth, it gets down to business. The damage to the US economy that is estimated to occur if emissions continue unchecked is huge. With continued growth in emissions at current rates, annual losses in some economic sectors are projected to reach hundreds of billions of dollars by 2090—more than the current gross domestic product of many US states.

The destructive impacts of unbridled warming have negative effects on almost every facet of human activity: water availability, human health, the welfare of indigenous peoples, ecosystems, agriculture and food security, infrastructure, the oceans and coastal zones, tourism and recreation.

NCA4 looks at the regional impacts of the changing climate.  Five of these regions are contiguous with Canadian provinces, and so the climate impacts projected for these regions can be reliably extrapolated to several Canadian provinces.

Baked Alaska?

Alaska is huge: almost one fifth the size of the combined lower 48 states.  Even so, it’s smaller than the Canadian territory of Nunavut, and actually not that much bigger than Quebec.

These far north regions have unique and special problems when it comes to climate change—due to weakening permafrost soils as warming increases. The NCA4 report estimates the cost of damage to infrastructure from $110 to $270 million per year, even assuming what it calls “timely repair and maintenance”.  The longer sea ice-free season, high ground temperatures, and relative sea level rise are expected to worsen flooding and accelerate coastal erosion leading to a loss of terrestrial habitat that may require entire communities to relocate to safer terrain. The impacts of climate change are expected to affect all aspects of Alaska Native societies: from nutrition, infrastructure, economics, and health consequences to language, education, and the communities themselves. This pattern of intensifying hazards and worsening impacts is likely to be replicated all the way across the Canadian territories of Yukon, NWT, and Nunavut.

Annual average temperatures in the United States are projected to continue to increase in the coming decades. Regardless of the future scenario, additional increases in temperatures across the contiguous United States of at least 1.3°C relative to 1986 -2015 are expected by the middle of the century. As a result, recent record-setting hot years are expected to become common in the near future. By late this century, temperatures could rise between 3° and 6°C if emissions continue to increase unabated. This scenario will certainly be replicated across most of southern Canada. This means more frequent and intense heatwaves–like the one that killed 70 people in Quebec earlier this year when humidex temperatures soared to 40°C in July.  Moreover, since the Arctic is warming twice as fast as regions further south, the impact on Canada’s indigenous communities and Arctic ecosystems is likely to be to be devastating.

Sea levels rising

The NCA4 report projects strong sea level rise along all US coasts, with increases of between 1.3 and 2 metres along the northeast coast from Virginia up to Maine. All the Atlantic Canada coastal cities, especially Saint John and Halifax are vulnerable.  Moreover, although Canada doesn’t experience too many hurricanes, with warmer Caribbean and Atlantic waters it is certainly conceivable that New Brunswick and Nova Scotia could soon be impacted by hurricanes that churn their way much further north than most of them do now.

The US is more vulnerable to extreme events than Canada.  The NCA4 report briefly summarizes the catastrophic impacts of the 2017 hurricane season : Harvey, Irma and Maria; the 2016 floods in Louisiana and West Virginia; the devasting droughts in 2015 and 2017; and of course the wildfires that every year seem to be larger, more intense, and destructive.

But less vulnerable doesn’t mean immune. With rising temperatures, drier conditions, and more frequent heatwaves, the extent and intensity of wildfires in Canada can be expected to worsen—just are they will in the US.

Will the stark warnings and grim assessments of the IPCC report on global warming of 1.5°C and the Fourth National Climate Assessment lead to a stronger government response in the US and Canada, and more vigorous action to reduce emissions of greenhouse gases?  In the US it seems unlikely. President Trump seems determined not to take climate change seriously.  In Canada, in light of these reports, one might hope that Justin Trudeau makes a renewed and stronger commitment to meeting Canada’s emission targets set under the Paris Agreement–targets that at this point in time look very much out of reach.


For the NCA4 Report-in-Brief, it can be found here.  And a good article with infographics from InsideClimateNews can be accessed here .     

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