What different degrees of global warming look like

Hi, it’s Gregor again, CTO of Datawrapper. Last Friday millions of people were protesting around the world, demanding more decisive actions on climate change from their governments. So I thought it’s a good time for another Weekly Chart on this topic…

Perhaps the most central aspect of our climate crisis is the fact that the greenhouse gases in the atmosphere are leading to a warming of our planet. The warming is already underway and it’s measured as global mean surface temperature. When you hear “we need to stay below 1.5 degrees of warming,” it’s this temperature that’s being referred to.

One big problem with this data is that when some people hear of 3°C warming they might think that that’s not too bad. On some cooler days in Berlin, many would even welcome a few extra degrees. But a global mean surface temperature increase of 3°C means an increase of the average of all temperatures, including summer and winter, Northern and Southern Hemispheres, land and ocean. Local effects of such warming are a lot more severe.[1]

Degrees of Global Warming

±0 +0.5 +1 +1.5 +2 +3 +4 +5°C 1900 1950 2000 2050 2100 “Hot-house Earth”: warming incompatiblewith human civilization, most of the planetbecomes uninhabitable, possible populationreduction to one billionSome summers so hot thatstepping outside could be lethal.High risk of food shortagesDeadly heatwaves every summer, hundredsof drowned cities, devastation of the majorityof eco-systems, more tipping points arecrossed, leading to intensified warmingHigh risk of reversing of carbon-cycle triggering runaway warming spiral.Droughts and famine for billions ofpeople, leading to chaos and warsMore extreme heatwaves, morefloods, more droughtsIncreased intensity and frequencyof extreme weather eventsLikely tropical crop yield declineand food supply instabilities5% chanceof stayingbelow 2.1°C5% chanceof reaching+4.9°C most likelyscenario+3.2°C most likelyscenario+3.2°C 201920th century average
The solid line shows 5-year average of global land and ocean temperature anomalies (NOAA). Dotted lines show different percentiles of warming predictions according to Raftery et.al, 2017. Inspired by The Guardian.

Chart choices

This chart is all about the annotations! I wanted to have a lot of room for them, so I extended the y-axis to the top and picked a very tall aspect ratio. The colored bands in the background (created with our range annotation feature) visually divide the vertical scale into different “heat zones.” To be able to use colors that really pop out, I used white as text and line color.

The text annotations mention some of the effects that will become highly likely under each level of warming. I ended up spending more time researching the annotations than creating the chart itself (you’ll find a lot of sources linked in the footnotes below[2] ).

Finally, I added some statistical projections for future warming that I found through this Guardian article from 2017. In contrast to some of the IPCC reports, the projections aren’t reflecting different emission scenarios, but are based on a model of our current emission trajectory (which already includes some mitigation measures).

That’s it for this week. As always, you can click on the “Edit this chart” button to use this chart and publish it. If you’re interested in our previous charts on climate change, we created a list of them here. And if you feel like it, there’s another global climate march on Sept. 27, 2019 (that’s tomorrow!). You can check out this map of marches to find out the one closest to you!

  1. For instance, a 4°C increase of global mean surface temperature is equivalent of a 5°C-6°C increase in global land temperature, which increases the temperature of the hottest summer days by 8-10°C in Central Europe and even 10-12°C in New York (source) ↩︎

  2. For more disturbing background about the consequences of climate change I recommend the books The Uninhabitable Earth (David Wallace-Wells, 2019) and Six Degrees: Our Future on a Hotter Planet (Mark Lynas, 2007). Most of the sources for the chart annotations I found through these books.