In Maryland, where I live, it sure has been warm this summer! My house was built in 1877 and thus has no central air conditioning. I generally gauge how bad a summer is by how often I have to install my window air conditioners, which has happened a lot this summer. Does that mean global warming is real? It depends. Sure, a bunch of warm days may definitely make it seem like the planet is warming. And the “un-winter” this past year might reinforce that conclusion. However, scientists generally look at the bigger picture to diagnose if we are seeing long-term changes.
Hot days are significant and they can indicate change, but true evidence comes from looking at averages across at least 10 years of data. In order to scientifically state that the climate is warming, we need to look across many days. This is where the controversy stems–but first, what do we already know?
There is one major certainty that we know for sure. When you put CO2 (carbon dioxide) into the atmosphere, the atmosphere warms up. Everybody agrees with the atmospheric physicists that this reaction is real. And there’s also no question that we’ve been putting lots of CO2 into the atmosphere.
As indicated above, the official record from the Summit of Mauna Loa in Hawaii tells us that CO2 levels are increasing. Here’s where it gets murky. The science of global climate change is extremely complex with a mix of physics, atmospheric science, and oceanography thrown in, since the atmosphere and the ocean have a very strong and complicated coupling. So, the question remains, what data is being used and what is the most accurate means to identify trends in global temperatures?
How Are We Measuring Temperature?
A major source of controversy is how we measure temperature. If you look at patterns in global temperature, it sure looks like it is increasing. However, one factor is what’s called the “tarmac effect.” Over the years, most climate monitoring stations have been moved from rural locations to airports. Anyone who has ever flown knows that airports have large expanses of black tarmac. This might artificially raise temperatures. The National Oceanic and Atmospheric Administration (NOAA) is attempting to avoid this effect with a new program called the Climate Reference Network, where sensitive instruments are placed carefully and consistently across the country. At this time, the program is not old enough to be able to give us accurate data about changes in the atmosphere.
The State of the Climate Now
Technically, we are still in an ice age! We can say that because there are still continental ice sheets covering Antarctica and Greenland. The future of those sheets has recently been called into question. New satellite data from Greenland shows that between July 8 and July 12 of 2012, 97 percent of the area of the Greenland ice sheet started to melt.
Of course, it takes warm air to melt ice. But, many scientists are stating that this is expected–the ice record in Greenland shows that this occurs about every 150 years or so, and we are right on schedule. It still takes warm air, and that warm air has to come from somewhere. And Greenland’s ice contains enough water to raise the global sea level by 7.2 meters (23.6 ft)!
I know that there are no answers here; my intention is just to demonstrate the complex nature of this ongoing and important debate. No one knows for sure what’s happening with the atmosphere. At the same time, everyone should stay attentive and like any good scientist, we should look at all of the evidence with a critical eye.
By Daniel Welsch, Ph.D.
Associate Professor and Program Director, Science at American Public University