The New York Times recently ran an article on climate tipping points. Anthony Watts, a climate change denier associated with the Heartland Institute, wrote a blog post claiming that,"...the entire New York Times article is nothing more than speculation with pretty graphics and that it heavily hedges its bets with weasel words such as could, may, might and possibly, but doesn't make a single solid prediction."Let's have a look shall we? Tipping points are examples of the more general physical phenomenon of hysteresis, which is also known as the path dependence of a system.
This means that the current state of the system doesn't just depend on its external variables, for example temperature, at a particular moment, but also on how you got to that moment. An everyday example is chocolate. If you melt chocolate and let it cool down again, it may reach the same temperature.
temperature that you started from, but the structure will be entirely different. I don't just mean the shape, which is now that of your inside pocket. I mean the structure and also the look of the chocolate will be different. The reason is that it'll have a different crystal structure.
It's a similar thing with butter. The state of the system, in this case the chocolate or butter, doesn't just depend on the temperature, but also on what happened on the way to that temperature. The change that happens if temperatures increase will not reverse as temperatures decrease. In the context of climate change, a tipping point likewise refers to a change caused by temperature increase that will not reverse if temperatures decrease.
The most obvious example is the melting of glaciers on top of mountains. Because you know, if temperatures drop, the ice isn't going to crawl back up. Glaciers take thousands of years to form. Yes, if temperatures will consistently remain cold, glaciers will grow again, but not as fast as they went.
There are also the massive ice sheets covering land in the Antarctic and Greenland. If those were all to melt, sea levels could rise 50 meters or more by 2300. At that point, much of Florida would be underwater, and for a sightseeing tour in London, you'd hop into red submarines. Besides the sea level rise, the melting of all this ice also greatly reduces the reflectance activity of large surface areas, which speeds up warming, so it's a positive feedback. A study came just out that says that the major mechanism for a major ice sheet collapse in Antarctica seems implausible, so that's good news. You might not need a submarine for London, a paddle boat will do.
Another example of a tipping point is the thawing of the permafrost, that's permanently frozen soil. it'll release potentially large amounts of methane that also contribute to global warming. That's again a positive feedback. And again, the methane isn't going to go back into the ground when temperatures drop. There was also a study on that a few months ago which found that the methane release would probably not be large enough to itself make a significant contribution to further warming.
That is, it'd probably not cause a runaway effect. If it was a runaway effect, that'd mean that the initial release would actually speed up further release. The new study says that this seems unlikely. So this is the second piece of good news today. Then there's the collapse of the ocean circulation in the Atlantic Ocean that I've talked about extensively before because it's constantly being confused with the Gulf Stream.
I'm enormously pleased that neither the New York Times nor Watts refer to it as the Gulf Stream. This circulation, known as the Atlantic Meridional Overturning Circulation, drives warm water and with that air to the northern part of the Atlantic Ocean. It's a major contributor to the comparably mild climate in Middle and Northern Europe.
Once it shuts down, it might take thousands of years to restart. Anthony Watts claims there's no evidence of that circulation slowing down. He doesn't quite seem to be up to date. because the evidence that something isn't right with the AMOC has increased since we last talked about it. There's a very interesting talk by Stefan Ramsdorff who used to say that the AMOC collapse was unlikely, but he's now changed his mind.
But what's major complaint about the New York Times article is that it doesn't make a prediction about exactly when these tipping points are going to be crossed. That's because the predictions for this are extremely difficult. But is this a reason to ignore them? Does anyone really doubt that frozen soil will thaw when it gets warmer or that ice will melt if temperatures continue to rise?
These things will happen if it gets warmer, whether or not we can name a date. It's exactly because we don't know when it'll happen that we should not gamble with further warming. But the scariest part is that climate models don't take into account their social and political feedback. The people who'll say, well, what's the point of reducing carbon dioxide emissions if the AMOC has collapsed anyway? We can't undo it, so we might as well not bother.
I think that's the tipping point we need to avoid most. The tipping of the public opinion from we can do it to why bother. So keep calm and keep dusting your solar panels. Did you know there's a free and easy way to learn more about the science behind all the videos that you've been watching? Yes, there is.
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