I confess I had difficulty grasping why climate scientists and climate modelers were so confident humankind was the main (not the only) contributor to the global warming that has been occurring for decades. My difficulty, frankly, was due to a degree of ignorance as to how these scientists had reached such a strong consensus.
It took some time and some research, but now I understand.
First, a few basic facts: Carbon dioxide is a potent greenhouse gas. It is a trace gas in our atmosphere, but has increased from about 280 parts per million pre-Industrial Revolution to a hair over 400 ppm today, which is about a 40 percent increase.
Methane is an even stronger greenhouse gas, which is being released by industrial activity, cattle flatulence (feel free to giggle), and the thawing of the permafrost in the Tundra, releasing large amounts of previously trapped methane into the atmosphere. As strong as methane is, carbon dioxide is a more important contributor than methane because its volume is much higher, and it stays in the atmosphere for more than a century. While water vapor is by far the largest volume greenhouse gas, a 40 percent increase in a relative trace greenhouse gas is very significant; carbon dioxide is now higher than it has been in at least 850,000 years. We know this through paleoclimatology; examination of tree rings, ocean and land sediments, and ice cores which go back that length of time.
In 2008, I attended my yearly American Meteorological Society conference in Denver. During that week, we spent part of the time at one of the world’s great "brain trusts" on meteorology and climate science, NCAR — the National Center for Atmospheric Science in Boulder.
After a number of lectures from leading climate researchers, they broke us up into small groups to spend some time with climate modelers — researchers who design, continually upgrade, and advance the now more than 20 climate models being used to project likely climate trends up to this point and into the next century. Here’s the gist of what I learned:
When climate models are run, they can be initialized with different data sets and different levels of greenhouse gas in particular. To a model, when these models are run with the carbon dioxide level of the year approximately 1900 (around 297 ppm rather than the current 403 ppm), and natural warming (not man-made) forces are maxed up, the globe would have shown slight cooling through the end of the 20th century. Left to so-called normal cyclic changes, even with other warming mechanisms in nature pumped up, no other explanation can be found for warming that has been ongoing at different rates over recent decades.
There are differences of opinion in the relevant sciences as to how much warming has occurred, is occurring, and will occur in the future, but warming itself is not in dispute.
I have a meteorologist Facebook friend in another city who used to sign off every post with “It’s the Sun, Stupid!”
He stopped doing that a few years ago. Now he knows the retort is: “No it isn’t, Dummy!”
Meteorologist Don Paul retired from Channel 4 earlier this year after more than 30 years on Buffalo TV. His articles on weather, climate and related sciences appear at buffalonews.com.