I am reading about the threat to the polar bear and that it is now listed on the threatened animals list.

Fair enough, I accept that with the ice melting there is less habitat availble, and that seal find it easier to escape etc...

What I fail to understand is that around 600 years ago, Earth was in the medieval warm period with temperatures much warmer than we have today.

Taking this as fact..... Why and how did the polar bears survive as I fail to believe they evolved in the last 500 years.

Regards

I am no expert on polar bears, but to my understanding, they have indeed evolved, and it is that evolution that is now putting them in jeapordy. The polar bear fur is an incredibly efficient insulator, and has only gotten better with generations. This protected them splendidly in their envioronment. In fact, it was a little too good, and it soon became apparent that a polar bears greatest danger was heat stroke. They simply couldn't dissipate excess heat fast enough. Now, on top of that, their environment is warming up. They were hot before, now it's going to get worse.

How do you know they didn't reach an endangered status around 600 years ago?

As you can see, even the medieval warm period was not as warm as it is today.

The hole in the ozone is up yonder and effecting the icecaps more directly? I read something somewhere recently that said the females averaged about half the weight they did in the 70's due to the ice melting and them losing hunting areas. Unhealthy mothers are sometimes unable to provide the milk then meat for the youngsters to survive so the mortality rate is quite a bit higher.

Maybe, nobody cared for polar bears 600 years ago? How do you know their numbers didn't drop during this time?

I would assume that the numbers dropped, and by reports today on how they are affected I could image they became extinct 600 years ago.

The fact that there are polar bears today is testiment that they survived the warm period previously, so what is different today?

Capeo>> Thank you for the graph. I wish I could lay my hands on one I had seen where the peak of today was level with the medieval warm period. This graph is showing today as the warmest in at least 2000 years. Stats are awkward.... There is still the graph around that denies a medieval warm period.

A lot of speculation on global warming and the ice caps. I am (was) merely curious as to the difference today as compared to 600 years ago.

The ozone layer is responsible for blocking harmful Ultra-Violet (UV) rays from reaching the Earth's surface, so when there is a hole in this protective layer, more UV rays are allowed to pass through. If you're exposed to these rays for too long they can damage your skin (sunburn) and cause cancer among lots of other problems. However the Ozone hole doesn't directly have anything to do with Global Warming.

Global warming is caused by greenhouse gases (such as Carbon Dioxide, methane, even the water vapour that makes up clouds) that build up in the atmosphere. Infra-red rays, heat, is emitted from the Sun and is able to reach the Earth's surface through the greenhouse gases, but they are then unable to bounce off back in to space as the greenhouse gases block them.

Which means the Earth gets warmer.

Because "endangered status" wasn't invented 600 years ago, and most of the world didn't know about them. Unless your refering to numbers going down to near extinction, I highly doubt they were reduced significantly, as the medieval warming was not nearly as bad. And I think the medieval warming for the most part was just in western Europe(correct me if I'm wrong).

Western Europe was affected quite significantly, although the trend extended across the Atlantic.

Even with the medieval warm period 600 years ago the earth still isnt going to get as warm as it will and is getting.

We are near approaching the hottest the earth has been in a millon years, when the sea level was 80 feet higher then it is today. Scientists are predicting that by 2040 the arctic ice cap will be completely gone during the summers. Polar bears do their hunting during the summers and hibernate during the winter. With no ice there will be no seals for them to catch and they will go extinct in the wild.

About half of all life on earth is threatened with extinction if the warming continues at its current rates. The polar bear is like a flagship signaling the worlds demise.

Don't tell that to the polar bears here in San Diego at the zoo. They are in an open enclosure, so they experience all of the weather here in San Diego, which has to be warmer than than anything at the poles.

The real problem is their habitit is being reduced because of all the melting.

The weather may be, but their refrigerated duck-pond most certainly isn't . Also, they get regular haircuts, which cancels out the biggest problem.

In all cases, it's hardly a one cause problem. Any animal (well, most) could adapt to one, maybe two changes, but start piling them up and chances of survival drop dramtically.

The zoo where I live lets the polar bears outside on certain days of the year...I know because I tried to climb inside to pet one once.

I don't think polar bears will become extinct if the climate becomes warmer. Global warming, if at all, will take place at a slow and gradual pace. It will not be a sudden drastic change. I'm sure the polar bears will adopt. Warmer climate can only mean more food for the polar bear. When the ice melts, it becomes easier for the polar bear to hunt seals and such. When there is good food supply, I'd say their chances of survival and adaptation are pretty good.

Ummm. Thats why for the first time ever scientists working in the arctic have discovered polar bears that have drowned. Due to the fact that there is no ice left for them to climb out on to and hunt for seals. They are raiding trash dumps in alaska because they are already straving. They have even seen cannibalism start amongst the bears, another thing they have never seen happen before.

Global warming is going to happen pretty rapidly, it already is happening. In the past 25 years about 70 species of frogs in central and south america have gone extinct because of global warming. We are on the brink of ecological collapse. The earth will be warmer then any point in the past million years if current trends continue.

The change is happening so fast that alot of species havent and wont be able to adapt.

Polar bears are strong swimmers. They can swim for several hours at a time over long distances. They've been tracked swimming continuously for 100 km at a stretch, so it is more likely the cause of death here is not drowning.

Bears are curious, and it is not uncommon for bears to explore trash bins and such, also, cannibalism is not uncommon in the animal kingdom, and it needn't necessarily suggest starvation -there are various reasons for cannibalism. Polar bears kill each other for population regulation, dominance, and reproductive advantage as studies reveal. Killing for food seems to be less common.

I don't believe global warming will bring forth rapid changes. Of course, like most species, polar bears too would find climatic changes difficult to adopt to, and even their numbers may reduce initially but I don't think it would be impossible for them to cope. Polar bears will simply migrate to colder places and find alternative food sources.

Indications (from sea bed cores) are that there was less ice than today in the Arctic during some parts the early/mid Holocene. Also, Greenland ice cores show that the temperature there has been warmer than today for the best part of the Holocene (the MWP was not, comparatively speaking, all that warm!)



However, polar bears never used to be hunted by human nor have their usual prey hunted by humans. Oh, and humans didn't used to pollute the arctic. Nor build town where the polar bears preferred to spend winter.

It is already happening at a very excellerated pace, that is the problem. Lack of ice makes it more difficult ot hunt seals as they hunt the pups hidden under the ice.
You are way off there.

Animals can't adapt that fast.

But it isn't heat stroke thats killing them, it's starvation.

Polar bears acquire alot of their food by means of Seals. Underwater seals have the advantage over the polar bears and will inevitably escape (majority of the time). When the roles are reversed, the polar bear is more efficient at catching the seal on ice, but with the ice melting there are more and more escape routes for the seal meaning lower chances for polar bears to capture food.

Excellent graph. Thank you for posting. I note a high point at around 1000BC where temperature appears to be below present. I wonder if or when we will hit that peak. Interesting to note that over the last 10,000 years temperatures have remained fairly constant.