29 March 2011
When Dealing with Climate, Perception and Reality are Sometimes Very Different
Posted by Dan Satterfield
Was it a bad winter?
Ask someone what kind of winter we have had here in the Eastern USA and you will probably be told it was brutal. Same for last winter as well, with the record breaking snow storms in Washington DC and the heavy snowfalls in the UK as well. Scientific reality, however, can be quite different from perception. Dr. James Hansen at NASA has put together a fascinating look at the reality of the global climate over the past four winters when compared to the average between 1951-1980.
You can pick any 30 year period for your climate average, and you should know that the NWS uses the past 30 years with an update every ten years. The 1951-1980 period has another benefit as well, in that it covers the years most of the population grew up (especially baby boomers like me who were born in 1959). In other words, your idea of what a normal winter is was very likely formed from the winters of 1951-1980 (if you are a baby boomer), and not so much if you were born say in 1980 and are around 30 years old.
Hansen’s 1988 prediction.
James Hansen, in his testimony to Congress in 1988, said that most people would be able to detect the climate is changing by the first decade of the twenty-first century. So, was he right? Take a look at his evidence, which is pretty persuading to anyone with an open mind on the issue.
First, let me explain what the graphic below really means. Hansen looked at the winters between 1951 and 1980 and divided the world up into 5 categories: very cold , cold, normal, hot, and very hot. He then compared the baby boomer climate of 1951-1980 with the past four winters. Read Dr. Hansen’s explanation below the image.
Here’s how Dr. Hansen describes it:
“Now we can check the degree to which the real world has lived up to this expectation [That winters would be noticeably different by the first decade of the twenty-first century]. The answer will vary from one place to another, so let’s make a global map for this past winter. Each gridbox will be colored red, white or blue, depending on how the local temperature this past winter compared with the categories established by the 1951-1980 climatology.
Figure 7 shows the result for the last four winters (summers in the Southern Hemisphere). To make the maps even more useful we use dark blue and dark red to show those places in which the temperature fell in the extreme (>2 standard deviations) category that occurred only a few percent of the time in the period of climatology1 . The extreme cases are important because those are the ones that have greatest practical implications, especially for nature. Species are adapted to climate of the past, so a change to more extreme climates can be detrimental, especially if it occurs so rapidly that species cannot migrate to stay within tolerable climatic conditions.
The numbers on the top of the maps are the percent of the area falling in the five categories: very cold, cold, normal, hot, very hot. In the period of climatology those numbers averaged 2%, 31%, 33%, 31%, 2%, rounded to the nearest percent.
Figure 7 reveals, for example, that the past two winters in Northern Europe both fell in the category of “cold” winters, but not extreme cold. The area hot or very hot (51-73%) far exceeded the area with cold or very cold conditions in all four years (14-27%).
Take for example the (N. Hemisphere) winter of 2010: 73% of the planet had a winter that was either hot or very hot compared to the average winters of 1951-1980.
Yes, I’ve used my favorite Richard Feynman quote too often here but I cannot pass it up in this case: “Science is what we do to keep from lying to ourselves”.