Climate Threshold

The news about global warming has been getting progressively worse, as detailed in a number of places, especially Climate Progress. It appears that severe climate change may be unstoppable, and could get much worse if we don't take immediate and drastic action to reduce our carbon emissions. This is largely due to the growing threat that permafrost will melt that contains the potent greenhouse gas methane, releasing it into the atmosphere. Within the next few decades, adaptation may be all but impossible for us and many other species; and for those species who can't adapt, entire ecosystems could collapse due to their absence. The Earth, for them and us, will become uninhabitable.

Both what we use and what we waste comprise our consumption of resources, and particularly our ecological impact (which I've been calling “consumption of ecological resources”; or, more recently, just “consumption”). Based on recent data, carbon dioxide emissions appear to be proportional to the square root of the cube of consumption (consumption to the 1.5 power), and the range of projected temperature rise due to global warming appears to be roughly proportional to the cube of consumption (the square of emissions).

Interestingly, the assessment by climate scientists of how much climate change we and other species can adapt to coincides with my estimate of our consumption of all global ecological resources (see “Habitability Limit”). If we somehow are able to keep our consumption growing, despite loss of ecological services provided by other species, we will drive them – and us – toward extinction, with the rapid increase in temperature acting as a proximate if not ultimate cause.

What I consider more likely is that our consumption and population will peak just before we can compromise other species' ability to maintain habitability. When our consumption drops to preindustrial levels, temperature may still be high due to the persistence of our previous emissions, the trapping of heat by the atmosphere, and the feedback effects we have unleashed. The populations of other species may not recover as expected for similar reasons: artificially modified areas take time to revert to natural habitat; devastated populations must breed and adapt to new conditions through evolution and learned behavior; and broken relationships between species due to death, migration, or ecosystem collapse may cause further devastation. Even if we manage to reduce our consumption without killing ourselves off, what to me is our most urgent priority as a species, the Earth will likely take a long time to heal.