Is all climate change caused by humans?

July 11, 2011 0 Comments

I am issuing a clarion call to make plans to enjoy the weather during the middle of this work week! Unless you are one of the folks who really enjoys heat and humidity (such as Don Clark, a radio personality who used to work in the area, who wanted 95 and humid as many days as possible), you will really enjoy the cool down over the next few days.

The weather wasn’t too hot over the weekend but it was humid. Highs will once again reach the mid to upper 80s today making it a tad bit uncomfortable. Then we are looking at highs only in the 75 to 80 range from Tuesday through Wednesday. Wednesday is looking like a particularly gorgeous day with plenty of sun and low humidity. So why am I wasting blog time on a couple of days in the 70s? Because the heat will be back on for this upcoming weekend, and it might last for a few days. Highs will be near 90 on Saturday and then reach the low 90s for Sunday and Monday. The humidity will be quite high as well during this time frame. The high heat might even last a couple more days into the middle of next week. It looks like these few days coming up from the 16th through the 20th or so could be the zenith of our Summer, of the warm season. Right now I am looking at somewhat tolerable low 90s for most of the heat wave, but if there is more sunshine than expected we could be talking mid 90s. The record highs for this time frame are in the mid to upper 90s so we will be close. One key to how warm it gets will be if there is any rain or thunderstorms. If we have enough rainfall (a couple more downpours later this week), then evapotranspiration will keep a bit more of a lid on the temps.

One thing you will no doubt hear a lot more about later this week and into early next week is anthropogenic global warming (AGW). Nowadays, almost every heat wave is blamed on AGW (aside: some researchers and science journalists have more recently and accurately portrayed heat waves as “possibly” being due to, or partially caused by AGW), and with high temps possibly hitting 100 and the heat index certainly rising above 100 for many locations in the center of the nation (maybe even Chicago) for several days in a row, the subject will no doubt be on the lips of many.

Having a heat wave and setting record high temps are not that noteworthy in and of themselves, but if we have more of such heat waves this year and in coming years, that would be in line with predictions from AGW computer models. Of course the general theory is that as carbon dioxide increases in the atmosphere, the temperature will go up. Tony re-capped the latest trend of emissions in this recent blog post. Special note, most emissions are no longer due to the U.S., they are from China. However, with an increasingly interconnected international society, it is hard to pin the blame on either the consumers or the producers.

Even though carbon emissions are going up, there is no guarantee that temps will follow suit in a linear fashion. In fact, abrupt climate change has occurred a few times in the past due mostly to changing ocean circulations, not so much from carbon dioxide density changes. It has been found that El Nino has not always been as prevalent as it is now. Besides changes in ocean patterns, there are many other factors which play into the climate system such as biosphere changes and sun activity. Although humans are a powerful force of change on the planet, we are not in complete control. Low sun activity such as was recorded during the little ice age and caused the demise of the Norse colonies in Greenland could return. Different rates of carbon storage within the different ecosystems, such as forests could make a difference. Tropical forests could end up storing a lot more carbon if they are protected (and more are coming under management). Even things as esoteric as cosmic rays could influence the future climate. After many years of ivory tower dismissals, research is giving more credence that cosmic ray flux can change cloudiness in the atmosphere.

Thus I am interested to see many people still trying hard to fit every small movement of temperatures into a human-caused scenario. Many of you are probably aware of the fact that 1998 was the warmest year on instrumental record and then global average temps declined slightly for the next 10 years. Perhaps it was a natural cool cycle super-imposed on a long term uptrend? I wouldn’t be surprised. But some want to argue that the “pause” in theoretical  AGW was solely due to human actions. At least one researcher has claimed that the slightly cooler trend over the last decade was caused by China emitting more sulfur dioxide into the atmosphere. Sulfur dioxide tends to block out sunlight and cool the earth. This happens naturally through the action of volcanoes.

Along with the trend of blaming every change in the climate on human action, as mentioned earlier, there is also a trend of associating every extreme weather event with AGW. I discussed the heat above. In addition, some scientists are claiming the big floods, fires, and deadly tornado season are a symptom of AGW and it will only get worse in coming years. Just anecdotally, it seems I have seen about the same amount of extreme weather during my lifetime, whether it was in the 70s and 80s or now. The only thing I have witnessed more of (again just anecdotally) is warm weather.

Have a good Monday! Meteorologist Justin Loew

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