So I had a nice discussion with a student, who was confused after receiving some opposing viewpoints on Global Warming from different professors in a relatively short time period. In one of the statements, I had claimed that there were more polar bears now than there were 20-30 years ago. In another statement, another professor claimed that the polar bears were dying off due to arctic ice retreat due to global warming. This is actually a nice case of "follow the data", where the problem is defined in a relatively concrete way. Another example of this is the question "is it warmer now than 1000 years ago?". On the second question, www.realclimate.org would say "yes, it is warmer than 1000 years ago" and cite the proxy data, etc... www.climateaudit.org would say (I believe) "maybe, maybe not" and cite the issues with the analysis of the proxy data.
Now, back to the polar bears. From the polarbearsinternational it is confirmed that the population of polar bears from the 1960's was very low, in the few thousands, and in the early 2000s was up to between 22000-25000. These are also reflected in the usgs site on polar bears where you can actually get some of the data.
If you go to the polar bear specialist group which advises for the IPCC, you can find a table of the status of the polar bear in various regions. The problem with this table is that there is a column titled "Observed or predicted trend". Hello? Why would you mix observed trends and predicted trends in a table? Just show me the data. Anyway, there is a document here which has an explanation of the projections, and possibly some data, although I haven't read the 200 pages of the document to see if it is buried in the text (there is no figure with the data...just model predictions). I'd love to find a straightforward presentation of the estimates of the current numbers of polar bears, complete with error-bars to denote uncertainty.
It seems reasonable that with the decline of the arctic ice that the polar bear populations can be affected, some more than others, but the role of hunting (the regulation of which caused the surge in the bear numbers from the 1970s) still plays a role can is difficult to disentangle...I've seen unsubstantiated claims that the areas with the decrease are primarily hunting areas. I haven't confirmed this, but this could also be the fact that ice retreat will be more substantial in the more habitable areas, where there would be more people. Correlation does not equal cause and effect.
So, it is a fact that there are many more polar bears now than, say 30-40 years ago. It can also be true, although I have difficulty tracking the data down in a readable form, that arctic ice retreat could impact polar bear numbers adversely.
One question that I have now is, if it was warmer 1000 years ago, is there evidence that there was a significant retreat of the ice back then? If that is the case, then the polar bear scare is just that...a scare. Again, many of global warming consequences that are being reported are tied to the question of the size, extent, and effects of the Medieval Warming Period. That's why, in my opinion, that is the most important question of all.
I found the Word.Docx that I was looking for yesterday. This is what I had started to write. I have some more information in regards to whether or not it was warmer 1,000 years ago, but want to check that data again.
ReplyDeleteAccording to the data you've provided, it appears that you are correct -- polar bear populations have (compared to 1960) increased. But has the polar bear population continued to increase within the past decade? Polar Bears International states population increase is a result of polar bear harvest restrictions put in place in the early 1970s. The populations had then rebounded from over-hunting. The sites you've provided (in fact, the entire USGS paper) state that although polar bear populations have increased since 1960, it has recently decreased in many regions due to the increased duration of the ice-free period over the continental shelf. Yes, the regions of declining numbers are also regions where people still hunt. However, (and maybe I’m being too presumptuous) even if it’s difficult to disentangle poaching, the hunters have been decreasing polar bear numbers from 1970 onward, unless international law has been greatly loosened within the past decade.
Though I was confused about whose data was correct, yours or Hong's, I'm even more confused about why you used the polar bear's population growth as supporting evidence for public scare. As I had suspected when I spoke with you after class on day, polar bear population growth is (at least somewhat) unrelated to climate but instead related to international policies. There are too many factors for anyone, from either side of the argument, to make any claims about polar bear populations. I laughed at the “Observed or Predicted Trend,” which I had actually noticed before reading further on your blog your own comments. I laughed because that’s ridiculous scientific behavior, and then I became really upset – a mix of sadness, pity, anger, and disgust –because it shouldn’t be called science. I understand why you bring up the data. However, though I agree that international policy should not focus on such vague and imprecise data, I also don’t think you should tell a classroom of impressionable students that global warming is bogus, and when they ask why, you reply that polar bear populations have increased. End of class.
ReplyDeletedecreasing polar bear numbers from 1970 onward, unless international law has been greatly loosened within the past decade.
Actually, depending on the region, there have been some increases and some decreases. It is also common in ecological niches that, after a removal of a force affecting a population (in this case hunting) that a new equilibrium is established. The population then surges past this equilibrium, and the comes back down. I do not take at face value that the decreasing total populations are entirely due to reduced ice. Perhaps it is, and it is reasonable that it is, but that doesn't make it true.
I'm even more confused about why you used the polar bear's population growth as supporting evidence for public scare.
...because I have seen news footage that uses swimming polar bears as evidence for global warming. It may even be in Al Gore's movie, although I'd have to check. I didn't use it as a scare, others have, and I just want to make sure that scares (if there are any) are legitimate, and are based on real data.
I also don’t think you should tell a classroom of impressionable students that global warming is bogus, and when they ask why, you reply that polar bear populations have increased.
two points here. First, going back to what I said, I am certain that (after possibly being a bit over the top, given all the other topics discussed that day), that I said that global warming was a much more gray area than others. I doubt this was remembered as clearly as the initial point, and it does point to the interesting problem of communication on hot-button issues. Small wording differences get interpreted as denial versus skeptic, and I think there is a big difference.
Second, I used the polar bear example because it has been claimed that the extinction of the polar bear is soon, and is a direct consequence of global warming. I am not entirely certain of that, and it is also quite clear from the data that there are many more of them now than 100 years ago over which we have seen the warming. It still may be true that there is an impact from climate, but I want to see the data connecting it.
As with all things, the devils in the details.