Human beings are an extraordinary successful species. We went from having less than million of us (all in Africa) a few hundred thousand years ago to now covering the globe at 8 billion strong. But all that success comes with a price. The energy we’ve harvested from the planet (mostly in the form of stored solar energy i.e. fossil fuels) has changed the atmosphere and is now pushing the climate system into an uncharted direction. Climate change poses considerable risks for the future (just ask any insurance company ). The magnitude of that risk is something scientists having been trying to figure out for a few decades. Over the last year or so we’ve got some good news and some bad news on the climate front. Today I wanted to briefly walk you through both.

Let’s start with the good news (and thank the gods for any good news about anything these days). In a paper published just a few weeks ago, scientists found that the most worst-case scenario they’d been using in their studies can be taken off the table.

So what exactly does that mean?

In order to standardize their modeling, over the last couple of decades climate scientists developed a suite of projections for how much CO2 would get dumped into the atmosphere via fossil fuel use. Since CO2 is the greenhouse gas we care about most for climate change, each of these scenarios would then get fed into climate models. The models were then used to predict what Earth would look like by the year 2100. It was like scientist’s had a menu of future human fossil fuel to use in their models. That’s where the good news comes from. The most extreme fossil fuel future - which led to the most extreme climate change - can now be seen as “implausible".

Of course, this being climate change with its endless climate denial, some people were quick to claim the news as evidence that climate change was always a hoax. That, of course, is not why the team eliminated the extreme scenario. Instead, they did so for the best reasons. Things changed becuase we changed them.

Despite our general lack of doing what’s needed about climate change, we have done something . We’ve slowed our use of fossil fuels and that reason - and only that reason - is the extreme scenario is now unlikely. It’s something to celebrate.

So what’s the bad news? Well while the most extreme emissions scenario is off the table we are still driving the Earth into a different climate state. A while ago, scientists and policy makers set a 1.5 degree ( o C) increase in average global temperature as a red-line that should not be crossed. That number came from looking at variations in average planetary temperature over the last 12,000 years. These were always less than 2 o C. Recently it was confirmed that humanity, for the first time, crossed that red-line . It looks like we’ll soon be moving past it on a permanent basis. That puts us and our descendants into truly planetary uncharted territory. That uncertain future includes “ tipping points ” which could quickly and irreversibly lead to dramatic new climate states.

So, we will take our good news we can find it but there can no doubt that we are headed into an ever more climate changed world. Our work is still ahead.