Climate change What do degrees of global warming really mean?

[Maciamo]

When discussing climate change, one thing that most people don't understand is what the degrees of warming mean. The global temperatures are currently at 1.4° above pre-industrial averages, but we see temperatures records shattered almost every day all over the world by 3, 4, 5 or even 10 degrees in many countries. One reason is the difference of temperatures above land and above water. The oceans make up 70% of Earth's surface and the air over the ocean doesn't heat up as much as above land.

Additionally, regions closer to the poles warm up much faster than those closer the equator, so increases in temperatures are much more noticeable at higher latitudes like Europe, Canada or Russia than in the tropics.

The BBC posted these maps in August.

You can see how at +2°C of warming the oceans remain around +0.5°C, while the north of Canada (where wildfires happened) and the north of Russia exceed 4.5°C of warming. At a global average of +4°C of warming, arctic regions exceed 7°C of warming. But even that is not clear enough. These are the averages for a whole year. Extreme heat records are typically beaten in summer. Already now, at +1.4°C, Canada beat records by over 10°C in summer. Imagine what it would be like with an all-year global average of +4°C. Summer in Canada could go above +20°C above pre-industrial averages, well over 45°C, meaning that all forests will burn (actually I think they will already have burned long before we reach +4°C globally).

 

[bicicleur 2]

I see the north pole is warming faster than the south pole, however the south pole also is warming faster than the tropic and temperate zones. How does that combine with the fact that the east Antartic ice sheet is actualy growing?

East Antarctic Ice Sheet - Wikipedia

en.wikipedia.org

furthermore :

in 2022, an extensive assessment of tipping points in the climate system published in the Science Magazine concluded that it would most likely be committed to complete ice loss only once the global warming reaches 7.5 °C: the absolute minimum level would be at 5 °C, but it could just as easily bet at 10 °C

 

[Maciamo]

I see the north pole is warming faster than the south pole, however the south pole also is warming faster than the tropic and temperate zones. How does that combine with the fact that the east Antartic ice sheet is actualy growing?

East Antarctic Ice Sheet - Wikipedia

en.wikipedia.org

The northern hemisphere is generally warmer because it contains most of the land mass (and as I explained above air warms up faster on land than above the ocean).

Not sure about the specific case of the East Antarctic, but overall there is no doubt that the Antarctic Ice Sheet has been decreasing too. In fact, Antarctic sea ice is at a record low.

Antarctica’s sea ice grew far more slowly than expected in the early parts of the southern winter. As a result, despite a spurt in early September, when the sea ice grew more than twice as rapidly as is usual, the ice now falls far short of the average maximum observed at this time of year. On September 7th it covered just short of 17m sq km, according to data tracking its daily extent from America’s National Snow and Ice Data Centre (nsidc). That is 1m sq km below its previous smallest annual maximum in 1986—an area equivalent to two Spains.

furthermore :

in 2022, an extensive assessment of tipping points in the climate system published in the Science Magazine concluded that it would most likely be committed to complete ice loss only once the global warming reaches 7.5 °C: the absolute minimum level would be at 5 °C, but it could just as easily bet at 10 °C

I am not sure why you mention this. There is no need for all the ice to melt for the results to be catastrophic. As I explained in this post, even at 2 degrees of warming, the sea level rise would displace about half a billion people. According to Carbon Debrief, at +4C the sea level rise would be between 6.9m and 10.8m. The sea level rise simulator does not even go beyond 4C of warming. If all the ice in Antarctica melted the sea level would rise by 70 metres compared to now.

 

[Maciamo]

These maps give you an idea of what a sea level rise of 70 metres would look like (around+7.5°C of warming). Denmark, northern Germany, the Netherlands, Flanders, all the Po valley in northern Italy and many other parts of Europe would be completely under water, with no chance of building dikes high enough to prevent it.

+7.5C of warming may seem quite remote from the present. Hardly anyone would think that it would happen before 2100. But then all "experts" and governments thought that it was possible to keep global warming under 1.5C by 2030 and it was already reached in July and August, with September shooting at +1.8C. Even the most pessimistic experts are shocked by what just happened. It wouldn't be far-fetched now if we reached +2C in the next few months. Nobody knows for sure why global warming has been speeding up the way in did in the last four months. And if it continues on this trajectory for a few more months, then +7.5C of warming is much more likely to happen before 2050. As I explained in this thread, temperatures have been rising over 30 times faster since June than anytime in the last 80 years.

 

[Maciamo]

Copernicus, the Earth observation component of the European Union Space Programme, just published the data for September. The Earth was 1.75°C warmer than the pre-industrial average. They have a map of the Arctic and Antarctic showing the temperature anomalies. In the Antarctic, there are huge regional differences. The Weddell Sea is colder than usual, but the landmass itself is warmer (as expected) and the Ross Ice Shelf is much, much warmer (+16°C).