“No amount of experimentation can ever prove climate models right; a single experiment can prove climate models wrong.”
– adapted from Albert Einstein quote.
To help understand global warming, I’ve whipped up some commonly asked questions and their answers (below) to help you better understand the issues involved.
As you will see, the science of global warming is far from ‘settled’. It is only because of the political and financial ramifications of global warming that so many people (mainly politicians and those who have vested interests) are trying to convince you otherwise.
IS GLOBAL WARMING HAPPENING NOW?
There is no way to know if warming is ‘happening now’. Because natural climate fluctuations on a year-to-year basis are so large, we will only recognize warming (or cooling) several years down the road when it appears in the rearview mirror.
The most important statistic to me is that global average temperatures stopped rising in 2001, as shown in the following chart of global tropospheric temperatures that John Christy and I derive from satellite measurements.
As you can see, we might have even entered a new cooling trend. The claim that the warming trend over the last 50 to 100 years is continuing right now, or that it is even ‘accelerating’ is pure speculation, based upon the assumption that what has happened in recent decades will continue into the future.
ISN’T IT WARMER NOW THAN IT HAS BEEN IN THOUSANDS OF YEARS?
Well, look at the following recently published proxy reconstruction of global temperatures over the last 2000 years. This graph is based upon 18 previously published temperature proxies, and so provides the most robust estimate available to date. It can be seen that significant warming and cooling periods of 50 to 100 years in duration seem to be the rule, rather than the exception. There were probably even warmer years during the Medieval Warm Period (MWP) than we have seen in recent years. Even the warmth of the ‘record’ warm El Nino year in 1998 (see temperature chart above) might well have been surpassed several times during major El Nino events that occurred during the MWP. Unfortunately, there is no way to know how warm individual years were a thousand years ago…the graph below is made up of thirty-year averages. I added the dotted line toward the end showing the modern thermometer record.
ISN’T DISAPPEARING SEA ICE IN THE ARCTIC PROOF OF MANMADE GLOBAL WARMING?
Warming, yes. Man-made, no. As can be seen in the following chart, it was just as warm in the Arctic (or nearly as warm) in the 1930s, with loss of sea ice and changing wildlife patterns reported in newspapers. The water levels in the Great Lakes reached record lows during this time, too…just as has happened again in recent years.
It should be remembered that we have had accurate satellite measurements of sea ice only since 1979, a period which has been entirely during the positive (warming) phase of the Pacific Decadal Oscillation (PDO, see graph below). The PDO is an index of weather patterns over the North Pacific Ocean that flips every 30 years or so. The coincidence that the satellite era started right after the “Great Climate Shift of 1977″ has probably biased what we consider to be ‘normal’ for global climate. In fact, based upon the 2,000-year temperature graph shown previously, one might argue that there is no such thing as ‘normal’ climate.
ISN’T ARCTIC SEA CONTINUING TO MELT FASTER AND FASTER?
No. As can be seen in the graph below (updated here through April 21, 2009), 2007 was the year when summer ice melt resulted in a 30-year record low in sea ice coverage. In 2008, the ice recovered somewhat. And from looking at 2009, we might well see further recovery this summer. Based upon the PDO index (above) it could be we have entered a new cooling phase of the PDO, which might explain this sea ice recovery, as well as our recent return to colder, snowier winters in the Northern Hemisphere.
AREN’T THE POLAR BEARS DYING FROM DISAPPEARING SEA ICE?
Generally speaking, no. While 2 sub-populations of polar bears appear to be threatened by the recent reduction in Arctic sea ice, the other dozen or more sub-populations are either stable or growing. Polar bears survived previous periods of Arctic warmth, and they will survive this one, too.
Polar bears, especially the cubs, tug at our heartstrings because they are so cute, and so make wonderful ‘poster children’ for global warming. What is ironic is that the polar bear is the only predator that will actively track down and eat a human being. The following two photos were sent to me by someone in Alaska…a polar bear that was waiting for a man to return to his truck.
You can learn the truth about the polar bear issue from a polar bear researcher here.
WHAT ABOUT THE COLLAPSING ICE SHELVES IN ANTARCTICA?
Just as Greenland glaciers will continue to flow downhill and break off into the sea as snow keeps falling on Greenland, the Antarctic ice sheet also slowly flows toward the sea. But in Antarctica, this forms ice ‘shelves’ that can extend out over the ocean a considerable distance. These ice shelves ring the entire continent, and eventually they must break off and float away. It could be that ice shelf collapse events become more common when warmer ocean waters affect a portion of the continent, as has been the case in recent years. Maybe a period of more rapid ice shelf collapse also occurred during the Medieval Warm Period of 1,000 years ago…we just don’t know.
