Lasers, Science and Global Warming

There is no consensus in the scientific community that global warming is getting worse or that it is man-made” – Ron Paul

It does make you wonder sometimes, doesn’t it, how theoretical statisticians in the middle of the largest snowstorm in New York City’s history could stand there and say, ‘I don’t care what it’s doing. It’s going to get very hot soon.’” – Newt Gingrich

The science indicates that human activity is not the cause of all this global warming. And that in fact, nature is the cause, with solar flares, etc.” – Michele Bachmann

Between 1991 and 2011 97% of all peer-reviewed articles on the subject have affirmed that climate change is real, and that it is human caused. When this is contrasted with the fact that some of the latest polls have shown only 40% of Americans and 54% of Canadians believe that anthropocentric climate change is a major threat, it becomes clear that we’re losing something in translation. And this loss could have serious repercussions towards our ability to push for strong policy decisions that could effectively combat the issue. Closing this gap between the experts and the general public is one of the main challenges that face environmentalists today, and why environmentalism is quickly becoming much more to do with public relations and effective messaging than science. The science has spoken and not nearly enough people were listening. The question now is why this is happening, and what can we do about it?

The first problem is that while the basic premise of green house gases and climate change is simple (specific molecules trap heat in the atmosphere and the more of these molecules that exist in the atmosphere the hotter the world will be), the actual science is incredibly complex, and our inability to adequately explain how we know what we know allows deniers to weasel doubt into the discussion. With this in mind, the Green Society Campaign is introducing a series of blogs specifically designed to explain how scientists come up with the information that informs the talking points. First up is one of the ways we currently measure the amount of green house gases in the atmosphere.

A few weeks ago I was lucky enough to convince Dan Maser, a Ph.D. candidate at the University of Colorado and employee of the National Institute of Standards and Technology (a division of the United States Department of Commerce) to attempt to explain to me the process that allows them to measure the concentration of green house gases in the atmosphere. The answer was as complicated as I feared, but I have made every attempt to make it understandable for those without a science background and have had this explanation checked over by Maser to ensure that I did not simplify to the point of lying. The very basic idea is that Maser and his lab use laser pulses to measure the concentrations of green house gases.

To understand what is going on, one must first understand the concept of frequency combs.

This video does an excellent job of explaining what a frequency comb is but for those who don’t like watching videos these are the basic things you need to understand.

1) Frequency combs are collections of sharp and precisely spaced radiation “teeth” with respect to frequency (this means that each tooth corresponds to a specific frequency).

2) Molecules in the atmosphere all have specific frequencies of radiation that they absorb.

3) Each laser pulse creates hundreds of thousands of comb teeth and that these different teeth have different frequencies.

4) Scientists use the frequency comb and measure how much of each tooth makes it through a particular distance of atmosphere and how much was absorbed by the molecules.

The experiment works by transmitting radiation frequencies that are in the region that many gases in the atmosphere absorb radiation. Due to the ultrafast (ultrafast basically means ‘very short’ but for a better definition go here) nature of the laser radiation, each pulse spans hundreds of thousands of comb teeth and these teeth span the wavelength ranges of many different molecules’ absorptions. Then, by measuring how much of each tooth gets transmitted (i.e. isn’t absorbed) through a particular distance of atmosphere, scientists can measure the concentrations of different green house gases.

The TL;DR version of this is that we fire laser pulses into the atmosphere, parts of those pulses are absorbed by green house gases and we know which parts of the lasers correspond to which molecules. So by checking how much of each part of the laser is absorbed we can measure the concentrations of green house gases. Scientists can then use this data to measure the increase of green house gases over time and how this increase correlates with average global temperatures. The TL;DR of this TL;DR is Lasers, Absorption, Science!

Stefan Hostetter
Stefan Hostetter

These are the things that scientists are doing all over the world to better understand climate science and the world around us. Taking this understanding and pushing for evidence-based policy is the required next step. Hopefully, a better understanding of just exactly what scientists are doing will allow for this kind of thinking to really take hold.

By: Stefan Hostetter

Green Majority Partner and Contributor

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