If things are truly that bad in 30 years when temperature is only a fraction of a degree warmer and sea level has barely moved - imagine how fucked we are in 200 years when polar melting is advanced, sea levels are many meters higher and temperatures are 4 degrees or more warmer than today.
I don't buy that claim though, it's hard to believe you could have a billion refugees with such tiny changes. We've already changed more than that since 1900 and there aren't a billion climate refugees. Why is the next half a degree of warming so much worse? I'd need to see what they base that estimate on.
One of the reasons why you can is that higher temperature move climate zones around. In particular they increase the size of deserts like the Sahara. Rich areas with expanded deserts, like California, can pipe in water from elsewhere. But areas like subsaharan Africa are a different story.
In short, it is easy to become a climate refugee from a little warming when that results in drought for you.
And some areas will get wetter. Higher temperatures mean overall more water in the atmosphere and overall more precipitation. That definitely makes winners and losers and refugees, but not in such huge numbers by 2050, or at least that would be very surprising and counter-intuitive.
>Why is the next half a degree of warming so much worse?
A 3 degree F fever is okay with some bedrest and ibuprofen, but a 6 degree F fever can kill you. There are breaking points in every system. Half the stress of a breaking point is usually fine.
This is true, but the percent change here is very small. I just find it highly improbable at best. I'm not going to buy into something so unbelievable without seeing a very strong line of evidence behind it.
No, change in temperature. From now to 2050 we're looking at a 0.5 C change in average temperature. You could also say change in sea level will be relatively small as well.
Averages are funny, and that's a global average so it's more pronounced at the higher latitudes. But still it's half of what we've already done since 1900. And as a percentage change in temperature in a given region, it should be fairly small.
Just intuitively it doesn't make sense that relatively small changes suddenly produce such disparate outcomes when they haven't to date.
Looking into the numbers a bit from what was shared above, I'm not wrong. 1 billion is the upper end of an estimate, with 5 million at the lower end. That's a very wide range.
> Just intuitively it doesn't make sense that relatively small changes suddenly produce such disparate outcomes when they haven't to date.
Average temperature by itself is a very misleading measure, because it does not tell you anything about how much energy is being added to the system. Different substances need different amounts of energy added to raise their temperature by 1 degree, a concept called heat capacity. The amount of energy currently being added (and not radiated back into space) to the planet is staggering, and far in excess of the ability of the oceans to absorb it: https://www.climate.gov/news-features/blogs/enso/role-ocean-...
I do not know why popular science reporting rarely mentions this.
I'm still not understanding -- how do you calculate an 0.5 C change as a percentage?
Edit: Regarding your other point, I'm sure you agree that an 0.5 C change from -0.25 to +0.25 will have a certain obvious dramatic impact. It might seem like I picked a particularly pathological example there, but if you imagine latitude on a globe or elevation on a mountain, you'll find somewhere (like the Laptev sea) hovering at that boundary and ready to cross it.
But that's only one boundary; there are many others, where the dominant plant or insect species changes from one to another, where methane gas starts to get released faster than stored, etc. So it's rather like a staircase, and when the average shifts, there's always somewhere on the planet that goes through a confusing and dramatic transition.
Average global temperature for the 20th century was 13.9°C. So 0.5C is a relatively small change, and less than half of what's already happened - and produced precious few climate refugees I might point out. I don't like using averages like that, as you rightly point out the difference in a particular region could be quite stark.
Ok, I see. So just so we're on the same page, for reference, the average surface temperature was thought to be 7.7 C in the last ice age. Converting both to Kelvin to account for the arbitrary zero point of Celsius, the 20th century was a 2.2% temperature increase relative to the ice age. Does your math agree?
I agree that a delta of 0.5 C is less dramatic than a delta of 6.2 C, but is your intuition in accordance with all that, and do you think percentage increases are useful here for building intuition? Where would you draw the line for "small" in terms of percentage change of temperature?
I also calculate that the Earth is 30% warmer than Mars, but you might want to double check my math.
Edit -- we could also consider that temperature is in most respects an exponential measure of physical quantities (E ~ e^kT). So the ratio increase in a physical quantity of interest (E2/E1) is already given, on a log scale, by an absolute temperature difference (T2 - T1).
I still stand by my intuition that if a 1 degree rise since 1900 didn't cause mass migrations, another 0.5 degrees seems unlikely to.
I think we can agree things are going to get worse and that kind of mass migration might happen over a longer time period. Just not in the next 30 years.
Why do you think your intuition is more relevant in the face of expertise about climate than the experts in the countless other fields you trust daily? Do you demand to see structural analysis reports before going into unfamiliar buildings?
I question things, the more outlandish the claim the more I question it. Experts are not always right you know. That's especially true on charged topics. I want to follow their line of reasoning and understand the claims more fully. And I was not wrong. If you see the post above going into more detail than the OP, 1 billion is the upper estimate, with 5 million the lower end of the range. That's a pretty wide range.
I don't see why people are giving me so much flak on this, the OP made a bold, unintuitive, and hard to believe claim - and people are saying I should be more gullible? More trusting of authority? Less skeptical?
As it turns out it's moot. The claim was the high end of a range starting at 5M. If your range is that wide you really have no business calling it an estimate. It's a WAG - a wild ass guess. I was right to be skeptical.
They may as well have just said we don't know how bad it's going to be, but it won't be good. And leave it there.
I don't buy that claim though, it's hard to believe you could have a billion refugees with such tiny changes. We've already changed more than that since 1900 and there aren't a billion climate refugees. Why is the next half a degree of warming so much worse? I'd need to see what they base that estimate on.