The recent spate of powerful hurricanes has increased the discussion of the impact of global warming (no, I’m not going to use the “polite” term of climate change, it is global warming) on our weather. While I am not an expert on the subject, since my research is in the solar atmosphere, I do read and understand quite a bit about the physics of atmospheric energy transport and our changing atmosphere.
There are many pieces of the puzzle playing together that lead to severe storms. The main point for severe storms is energy. To get high winds and water being carried from the ocean into the atmosphere requires energy. This energy comes from the Sun. The energy is emitted by the Sun, reaches Earth, passes through the atmosphere and reaches the ground or water, where it heats both. The heat can be felt and is infrared radiation. Some is radiated out into space while some is absorbed by the atmosphere, which then becomes mechanical heat. The proportion that escapes to that which is retained depends on the molecules in the atmosphere. The molecules that capture the heat are called absorbing molecules – the more there are, the less energy escapes the Earth and the warmer it gets. This increased retained energy can go into storms and make them more severe.
Some people have argued with me that these molecules are only a few parts per million, how can that make a difference? While a few parts per million is a small absolute number, it is a large percentage and changes a very delicate balance. An example of a small number having a big impact concerning physics would be water and ice. At 33 degrees Fahrenheit water is liquid, lower it to 31 degrees and it changes to ice, small change big difference. So yes, adding a “small” amount of absorbers to the atmosphere makes a big difference in the energy balance.
Another related result of the warming is an increase in ocean temperature. Temperature is heat is energy. So, we are adding energy to the ocean which makes it evaporate more water into the atmosphere (read rain), and this water is warmer (read energy and wind). The total result is that a storm that would ordinarily form anyway gets more water and more wind than it would have without global warming. We recently had a storm that went from category 2 to category 5 in a matter of hours. In my 74 years of life, I have never seen such a large change in such a short time. The reason for the rapid increase now is that there is much more energy going into the storm.
There are many other impacts of global warming that do not relate to hurricanes. Some regions become cooler because of the local conditions and various means of energy transport. Some regions become wetter and some dryer depending on the total systems effects as determined by the physics of energy transport. Some deniers have picked regions that have become cooler to say that warming isn’t happening. Others have pointed out that the Earth has been getting warmer since the ice age, so it’s just normal. The main point here is that the rate of warming has increased dramatically since about 1950, this increased rate tracks the increased rate of atmospheric pollutants.
A disturbing aspect about the scientists I know of who are climate deniers is that their research is funded by right-wing (read oil company funded) think tanks. One should also keep in mind that the congress of the last ten years would prefer to fund scientists who say that global warming isn’t a human-made problem. President George W. Bush even made government workers change the words global warming to climate change. The public should keep in mind what happened concerning the tobacco companies and public health in the 1900s. Greed is a very forceful motivator.
So, while I would not necessarily blame the increase in number of hurricanes on global warming, I would be willing to blame the increase in the number of severe hurricanes on global warming. We as a species need to take more responsibility for what we do to the planet.