jawagord wrote:
Who would accept a 20 year period as the normal condition, when we have very well known 30 year, 60 year, 100 year cycles in our climate? 20 years is nothing in climate, using data like this has led people to make ridiculous claims like an ice free arctic that should be happening right about now if the outlandish forecasts of a decade ago were to be believed.
It is not that they want to use just twenty years it is that it is the best data they have. Prior to that you have weather station data but type and accuracy of collection vary a lot and some ship captains logs from both Naval and whaling industry ships but again not their main business so not always accurate and mostly limited to where they found the edge of ice that voyage. A lot of weather data was collected at railroad stations which also held a telegraph office which put them downtown with a heat island effect to say nothing of the steam and smoke coming off the trains. And when it comes to the true arctic there was literally no one living there that could read or write much before 1900 other then a summertime whaler.
So now you are looking at proxies like ice core and pond sediment or tree rings all of which have limitations to trust worthiness.
People like to think that human interference with the climate started with the industrial revolution around 1830 but in fact humans have been altering the land and climate from biblical times. Once rich farmlands of the middle east have been turned to desert by poor farming and irrigation practices and much of Europe was deforested keeping cities warm from Roman times through the middle ages.
Here in North America the native Americans routinely burned large tracts of forest every few years to increase game populations and ease the hunting for them.
But of course all that doesn't hold a candle to burning 85 million barrels of oil a day after the invention of the automobile. So it is a pretty good bet that burning that oil and coal is what is causing the arctic ice to decline.
Thousands of Northern Hemisphere lakes are losing ice cover.
Can't prove that by me. Local lake had ice over two feet thick when I went ice fishing a week ago. Drove the truck right out to the shanty. Smelt were biting good.
