Getting Serious About Climate Change
Its time we grew up and faced the facts: climate change is real and its man made. By measuring the amount of CO2 we have put in the air and the rise in global temperature, we can estimate future climate changes. The results are not pretty.
Getting Serious about Climate Change
If you take a boat up the Dalyan River in Turkey you will pass the ruins of the Carian city of Kaunos. Kaunos used to be a nice place to live, with a bustling market, fantastic views of the river and the Med, an amphitheater, a large church, baths, and villa-lined streets. But farming and wood collecting led to erosion and the harbor silted up. Things got so bad that Kaunosites were called 'yellow-eyes' because of the malaria their swampy surroundings fostered. Eventually everyone left, and Kaunos passed into history.It is easy to imagine the city elders debating during the city's long decline. Some would argue that the hill sides should be preserved with various ordinances, others would say that the silting problem is overblown, and how do we know it comes from erosion anyway? And an ex-elder would be awarded laurels for producing a play called "Silting: an Inconvenient Truth".
I think of Kaunos whenever climate change deniers like Fox News, or Czech president Vaclav Klaus, or Sarah Palin, or Senator Inhofe spread their nonsense. And it appears that climate misinformation is having an effect on the public: Pew surveys consistently show that 40% of Americans do not believe in man-made climate change.
I want to stress that we are talking about climate here, not weather. Weather is day-to-day and quite erratic. Climate is long term trends in the weather. Noting that it has been a cool summer has next to nothing to do with climate trends.
Climate change is real and it is certainly caused by us. We can be sure of this because the average temperature of the earth is set by simple physical laws. You are familiar enough with these laws that you can judge for yourself where you should sit in the climate debate. Let's take a look.
You probably know that the temperature of something, say a frying pan on your stove, is determined by the jiggling motion of the atoms that make up the pan. The more jiggling, the higher temperature.
But what is it that determines how much atomic motion there is in the first place? The answer is given by balancing the energy budget. As energy is pumped into your frying pan, its atoms become increasingly agitated. They deal with this by dumping energy, either as heat into the surrounding air or as thermal radiation. Thermal radiation is a low frequency version of light that is invisible to our eyes, but can be detected by special cameras (maybe you've seen thermal images before). The amount of dumped energy goes up very rapidly with temperature, eventually as much energy is emitted from your frying pan as is pumped into it, and it reaches a steady state temperature.
Thermal radiation plays a crucial role in regulating the earth's temperature, as we shall see. But first, let's consider another familiar situation, namely your car on a sunny day. You know it can get very hot in there. Why is that? The sunlight entering your car carries energy and when it impacts pleather and vinyl (I'm assuming you have a 12 year old Dodge like me) it stirs up the atoms making up that substance. This stirring up is registered as heat by our senses. So far so good, but we are missing something important: we know the air in your car is warmer than the outside air. What's going on? The outside air (and the ground) is being hit with as much sunlight as the air and vinyl in your car! The answer lies in some tricky properties of glass. Glass lets light through (it is, after all, transparent) and it reflects some light. Some of the light that gets into your car is reflected by the interior (that is how you can see it) and the rest goes into heating vinyl. As before, all of those stirred up atoms emit thermal radiation. Now here's the catch: windshield glass is transparent to visible light, but does not permit thermal radiation to pass easily. Thus the thermal radiation is trapped in your car, causing the interior to heat up more than the exterior. The net result is a steering wheel too hot to hold: I am afraid that your car has a greenhouse windshield problem.
Your car is a pretty good facsimile of what is happening to the earth. Every day the earth receives a certain amount of light energy from the sun. Some of this light energy is reflected back to space. About 50% of it gets through to the surface, where it heats the planet and powers life. And just like in your car, the heated ground and oceans give off thermal radiation, and just like your car, much of this cannot get back out to space. In this case the role of your windshield is played by the atmosphere. More specifically, it is played by certain crucial gasses in the atmosphere: water vapor, carbon dioxide (CO2), and methane. These are the 'greenhouse gasses'.
Make no mistake, the atmospheric greenhouse effect is very important. By measuring energy flow, we can deduce that it raises the average temperature of the earth some 60 degrees. The atmosphere is earth's enormous puffy quilt. It would be very cold, and hard to breath, without our wonderful quilt.
What happens if you suddenly increase the amount of greenhouse gasses? Unless something else changes, more thermal energy is trapped in the earth's atmosphere and the average global temperature goes up. This is a consequence of energy balance and there is no way around it.
Those are the ground rules, now for some facts. The measured amount of CO2 in the atmosphere has gone up from 280 ppm (parts per million measured by volume) to more than 380 ppm in the past two centuries. It has gone up 17 ppm in the past 10 years alone. The extra 100 ppm represents about 760 billion tons of additional CO2 in our atmosphere. In the same period we have burned about 330 billion tons of fossil fuels, generating about 1200 billion tons of C02 (can it be _more_ than the amount of coal? Yes. Carbon atoms from the coal combine with two oxygen atoms to make CO2, leading to more weight). About 60% of that (720 billion tons) stays in the atmosphere. The rest ends up on our window sills and buildings and in our lungs.
Direct measurements of CO2 are shown in red. Estimates of earlier C02 concentrations are in green and blue. Notice the good agreement between proxy and direct measurements.
The figures add up and there is no question: generating the energy that drives our standard of living has raised atmospheric C02 concentrations by 100 ppm.
Currently we are burning fuel at a rate that adds 2 ppm of CO2 per year to the atmosphere. That's amounts to 14 pounds of CO2 pumped into the atmosphere by every person on earth every day of the year. If we focus on Americans and include all greenhouse gases, this figure bumps to 140 pounds per person per day. I suspect the atmosphere would be a lot less polluted if we each had to deal with 140 pounds of schmutz every day.
What does dumping our garbage into the atmosphere do to the temperature? The energy the earth receives from sunlight is equivalent to putting a 100 watt light bulb every square foot over the entire surface of the planet. Imagine all those light bulbs covering the earth and remember how hot one of them can get, and can you appreciate how much energy the sun supplies. This energy heats the earth and is ultimately re-radiated back out into space.
The additional CO2 makes for a cozier atmospheric quilt and is equivalent to changing our 100 watt light bulbs to 100.3 watt light bulbs. This does not sound like a lot, but it increases the average global temperature by about 2 degrees. Direct measurements show that the earth's average temperature has increased 1.5 degrees since 1900. Unfortunately, earlier temperature readings were not widespread enough to provide global averages. A warmer earth means smaller ice caps and thermally expanded seas, which raise the sea level. Again, measurements show that the seas have risen seven inches in the past century. Similarly, there is less average snow cover, birds breed earlier in the spring, and plant ranges are spreading northwards. If you are up to it, you can find thousands of pages of more detail at the Intergovernmental Panel on Climate Change web site.
Measurements of the global average temperature (black points and blue line). The colored lines are linear fits to the data. The fit temperature increase from 1909 to 2009 is 0.78 degrees C, or about 1.3 F. The actual temperature raise is 1 C = 1.8 F.
As uncomfortable as these facts are, things will get worse. The world has approximately 900 billion tons of coal left. Burning all of this (as recent experience with water shortages show, it would take an act of unprecedented courage and foresight for humanity _not_ to burn everything) will add an extra 3000 billion tons of CO2 to the atmosphere. This is expected to happen by 2065 with current consumption patterns. (Yes, all the coal will be gone in your children's lifetime.)
What is less certain is what a warmer planet means. The problem is that predicting climate is not easy. Nevertheless, when the experts run their computer simulations some clear trends emerge. The earth's average temperature will raise 9 to 11 degrees over preindustrial averages. Almost everywhere will be warmer with northern latitudes experiencing the largest effect. The exception appears to be Patagonia, which stays nearly stable. Rain patterns will shift, with dry places like the Southwest becoming dryer. Sea levels will rise by at least 12 feet and the oceans will become more acidic. The net result will be huge migrations of plants, animals, and people. If it happens slowly enough, things may not be so bad. If it happens quickly humanity will be placed under tremendous stresses and the results will not be pretty. Darfur, Rwanda, and Bangladesh may be providing glimpses of our future.
Satellite sea level measurements (blue) along with old tidal measurements (red).
If we decide that climate change is bad, some serious decisions will need to be made. Half-hearted measures are going to accomplish little, we essentially must stop burning coal and oil right now. I think we have no hope of achieving this and must go for the next best option: developing viable large scale renewable energy sources as quickly as possible. About the only good news is that coal and oil will be gone soon anyway, so we may as well get to work now. Energy will be expensive, but at least we will have it, and most of our standard of living. The other option is that our grandchildren return to a world powered by donkeys and water wheels.
The Kaunosites could always move up the coast; we have nowhere to run. The sooner we
start facing facts, the better.
