Climate Primer #18: Impacts of Climate Crisis – 1. Global Heating

To summarize, climate crisis is the defining issue of the century. Buildup of anthropogenic greenhouse gases (GHGs) in Earth’s atmosphere is driving global heating, while a convergence of global crises threatens to rupture key planetary boundaries beyond which organized human life on Earth would be threatened. Although the human activities which drive these converging crises (for simplicity: the climate crisis) are diverse and complex, the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) breaks down the sources of anthropogenic GHG emissions into five high-level sectors. Similarly, the impacts of climate crisis – in their variety and complexity – are almost impossible for an individual to grasp, but I’m at least going to highlight some of the key impacts in posts that will likely run for the next month or so.

(Note: Given that previous posts have already touched on the nine planetary boundaries as defined by the Stockholm Resilience Centre – namely stratospheric ozone depletion, biodiversity loss, toxic substance contamination, climate change (the defining sub-category of climate crisis), ocean acidificationfreshwater consumptionland system change, disruption of the nitrogen and phosphorous cycles, and atmospheric aerosol loading – I’m not going to specifically address these meta-impacts again, and will instead focus on sub-phenomena of these highest-order crises.)

So, where to begin? Again, the overwhelming complexity and sadness of climate crisis are among the key barriers to the initiation of climate action at scale. To make this process easier on myself, I’m going to follow the same approach I have in previous sub-series and rely on a trusted source, in this instance, once again AR5 of the IPCC. Feel free to ignore the text in the following image if the jargon is too much for you:

Source: AR5 of the IPCC (page 60)

To put it simply, in a best-case scenario, global mean surface temperature (GMST; the average global temperature) increase will be kept below 1.5º Celsius (which is the aspirational goal of the 2016 UNFCCC Paris Agreement) for this century. In less optimistic scenarios – as laid out in 2014 by the IPCC authors – GMST increase will likely exceed 2º Celsius. That may not sound like a big difference, but I think most of us now understand that – in terms of what it will mean for life on Earth – it is. Unfortunately, many rather level-headed sources are also now suggesting – as outlined in the excerpt which follows from Bill McKibben’s recent New York Review of Books piece – that without drastic action this decade, GMST increase this century could far exceed 2º Celsius:

Two degrees will not be twice as bad as one, or three degrees three times as bad. The damage is certain to increase exponentially, not linearly, because the Earth will move past grave tipping points as we slide up this thermometer.

You may be thinking: Didn’t the world leaders who signed the Paris climate accords commit to holding temperature increases to “well below” two degrees Celsius, and as close as possible to 1.5 degrees? They did—in the preamble to the agreement. But then they appended their actual pledges, country by country. When scientists added up all those promises—to cut emissions, to build renewable energy, to save forests—and fed them into a computer, it spit out the news that we are headed for about a 3.5-degree rise this century. And not enough countries are keeping the promises they made in Paris—indeed, our country, which has produced far more carbon than any other over the last two centuries, has withdrawn from the accords entirely, led by a president who has pronounced climate change a hoax. The En-ROADS online simulator, developed by Climate Interactive, a nonprofit think tank, predicts that at this point we can expect a 4.1-degree rise in temperature this century—7.4 degrees Fahrenheit. All of which is to say that, unless we get to work on a scale few nations are currently planning, Lynas’s careful degree-by-degree delineation is a straight-on forecast for our future. It’s also a tour of hell.

That’s probably enough for today. It’s obvious, but the clearest impact and signal of climate crisis was also the first to be named and reckoned with – global warming (or now, global heating) – and just as buildup in Earth’s atmosphere of GHGs drives global heating, global heating in turn drives many of the other impacts that will be explored in posts to come.

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