Impacts: How hot could it get?
Image @redcharlie
Does it really matter if it gets this hot?
It’s not just the amount of warming, it’s the speed of change. The planet hasn’t warmed this fast since the comet wiped out the dinosaurs at the end of the Cretaceous, 65 million years ago. Most plants and animals alive today—including humans, which have been around for only about 200,000 years—evolved to live in an atmosphere where the quantity of greenhouse gases keep in enough heat, but not too much. Adding so much more heat in just a few hundred years has changed the climate too rapidly for many plants and animals to adapt. This is disrupting entire ecosystems, bringing pests and diseases into new areas that aren’t adapted to them, driving species to extinction (Fig. 4) and threatening multiple life-supporting ecosystem services that we cannot exist without, which is why climate change is an existential threat.
“Ecosystems, species, wild populations, local varieties and breeds of domesticated plants and animals are shrinking, deteriorating or vanishing. The essential, interconnected web of life on Earth is getting smaller and increasingly frayed. This loss is a direct result of human activity and constitutes a direct threat to human well-being in all regions of the world.” – Prof. Settele, Global Assessment Report on Biodiversity and Ecosystem Services
“More frequent and intense extreme events, superimposed on long-term climate trends, have pushed sensitive species and ecosystems towards tipping points, beyond ecological and evolutionary capacity to adapt, causing abrupt and possibly irreversible changes”. – IPCC; Climate Change 2022: Impacts, Adaptation and Vulnerability
What’s the difference between 1.5°C, 2°C or a bit more?
The temperatures in Figure 1 are global averages, not maximum temperatures. At the poles, due to feedback effects, average temperatures are up to 4 times higher. This is already triggering cascade of dangerous tipping points, over which we have no control, which affects us here in Aotearoa, and which we cannot undo.
Think of it this way. Add 4°C to parts of the Greenland ice cap that were once -3°C. That’s now melting vast areas, adding to sea levels rise. Elsewhere in the world, just 0.5°C changes the way many plants and animals behave, which brings big problems for biodiversity and agriculture, and the spread of diseases. Adding just 0.5°C of warming increases the frequency of warm extremes over New Zealand from 93% to 234% (Fig. 4). That means even more frequent and more powerful storms, droughts, floods, and marine heatwaves.
Every fraction of a degree counts.
Carbon Brief has extracted data from around 70 peer-reviewed climate studies to show how global warming is projected to affect the world and its regions, based on 1.5°C, 2°C, and even higher warming (based on our current emissions pathway). Figures 4 and 5 are examples. Click on any image to see the full range on Carbon Brief’s website.