The “carbon budget” is an estimate of how much CO2 we can still emit, but still have a good chance to keep global warming from going over the 1.5°C limit into “dangerous” territory. The budget has recently been revised (upward, thank goodness) to about 420 GtCO2 (420 billion tons of carbon dioxide).
Staying within the 1.5°C limit doesn’t make us “safe” — there are still consequences of climate change, dangerous and costly, and we’re already paying the price despite not having hit 1.5°C yet. But going above 1.5°C takes us into what is best described as: nobody wants to go there.
With winter snow in the northern hemisphere, we tend to forget the heat that summer brings to the southern half of the world. It can get pretty hot down there. The Guardian reports that Australia is entering the third day of another terrible heat wave, remarkable not just for how hot it is, but how much of the country it covers: basically, all of it.
Like most people, I live on land, not at sea. I even live in the northern hemisphere.
Global warming isn’t the same everywhere. In particular, it’s happening faster on land areas than over the oceans. While the globe as a whole is warming at a rate of around 1.7 to 1.8 °C/century over the last several decades, the land areas alone have been warming up more than 50% faster, at about 2.8 °C/century. And of course, not all land areas are warming at the same rate either. On the whole, the northern hemisphere land is warming faster than southern hemisphere land; here in the north we’re heating up at around 3.2 °C/century (for land areas, I like to use the data from the Berkeley Earth Surface Temperature project).
One of those things, which happened to come up in conversation recently, is that climate change has its most profound effect on extreme events. Climate change is a change in the probability function (the odds for each possible outcome) of weather, and when you look at probability functions you find that if they change in the way we expect them to, it can increase (or decrease) the chance of extremes by a surprising amount.