Issue Position: Global Warming

Issue Position

The above graphic represents temperature recordings from 39,390 weather stations starting in 1800. At first, not much of the globe is colored because there were not many weather stations in 1800. Darker blue indicates temperatures below average. Darker red indicates temperatures above average. This data is taken from the Berkeley Earth Surface Temperature Study (berkeleyearth.org). It addresses all concerns raised about three previous efforts to measure the temperature of the earth (e.g., quality of data, urban heat islands, etc.). (Source: berkeleyearth.org.) All four major studies of the temperature of the earth are in close agreement. Since the 1800's there has been a temperature increase on land of about 1.6°F. The oceans absorb heat better, so the planet-wide increase has been about 1°F.

The Intergovernmental Panel on Climate Change (IPCC) lists 10 other observations that it regards as highly likely indicators of warming. Conspicuous among these are the increase in sea level (water expands as it warms), and the decrease in snow or ice cover.

The "greenhouse effect" works like this. Ordinary glass passes visible and ultraviolet light that comes from the sun into the greenhouse. This light warms the inside of the greenhouse. The warm inside emits infrared light. Infrared light is absorbed by glass. Think of the glass as being black to infrared light. It is warmed by infrared light just as any black surface is warmed by visible light shining on it. In this way, light enters the greenhouse but cannot easily escape from it, warming the greenhouse.

The "greenhouse gasses" are carbon dioxide (CO2), methane (CH4), and several other less important gasses. Most of the light reaching the earth is visible or ultraviolet light that passes through the atmosphere without being absorbed. This light warms the surface of the earth. The warm earth emits infrared light, which is absorbed by greenhouse gasses trapping the heat near the earth.

The CO2 and CH4 that humans are pouring into the atmosphere must be warming the earth. However, there are also variations in the temperature of the earth that depend on the earth's orbit and the intensity of the sun. So, the questions are, "How much of the warming is due to humans, and what is likely to happen in the future?" There are two approaches that lead to the conclusions that 1) greenhouse gasses produced by humans are causing most of the increase in temperature and 2) they will produce unacceptable warming of the earth.

The first approach looks at the history of the earth and asks how its temperature has varied with the concentration of CO2 in the atmosphere. There are a variety of sources for this information. The easiest to understand is the evidence from ice cores in the arctic and antarctic. There is an annual variation in the acidity of the snow that falls near the north and south poles. As the snow becomes compacted into ice, it forms layers of alternating acidity. If you drill a core of ice, the layers can be counted like the rings on a tree to determine how many years ago the ice was formed.

Next you can determine the concentration of CO2 in the atmosphere because bubbles of air get trapped in the ice, and you can measure the concentration of CO2 in the bubbles.

Once you have a record of changes in CO2, you can determine the historic temperature of the earth in the following way:

Oxygen comes in two forms, or isotopes. Oxygen-18 is about 12% heavier than oxygen-16. Water evaporates from the tropical ocean into the air. The air carries it toward the north or south poles. As rain forms, water molecules made from heavy oxygen fall out faster than water molecules made from light oxygen. So snow at the poles has less heavy oxygen than rain in the tropics. However, as the temperature increases the amount of heavy oxygen that reaches the north or south poles also increases. This allows us to determine the temperature of the earth in very ancient times. We can do it from the ratio of oxygen-18 to oxygen-16 in ice cores.

We can now compare the amount of CO2 in the air with the temperature for many years in the past. We find that warming always follows increased CO2. (Source: J.D. Shakun et al. Nature 484, 49--54 (05 April 2012) doi:10.1038/nature10915)

The second approach to understanding the link between CO2 production by humans and the climate involves scientific models. There are several factors that affect the temperature of the earth. The intensity of sun light varies in a regular cycle, as does the angle of the earth's axis. These things affect temperature. However, climate models indicate that these cycles should be cooling the earth. Climate models not only indicate that the rise in CO2 satisfactorily explains the rise in the earths temperature, they suggest details of the rise in temperature such as the fact that the stratosphere (the high altitude part of the atmosphere) is cooling while the troposphere (at the surface) warms. (An increase in the brightness of the sun, if there was one, would be expected to warm both.)

Burning fossil fuels pumps CO2 into the atmosphere producing changes that are not easy to reverse. Even if we stop burning fossil fuel today, the earth will continue to warm for at least a century because of the CO2 that is already present. Depending on how governments respond to greenhouse gas emissions, the IPCC estimates that the average global temperature will rise by 3.3°F to 12°F. You can click here for a list of a few of the problems the IPCC says rising temperatures will cause, even if governments restrict emissions.

Scientists have been accused of exaggerating the climate change problem to get more grant money for their research. In fact, the concerns expressed by organizations like the IPCC have been extremely conservative. Many scientists are concerned that things may get much worse much faster than expected. Polar ice has been melting and the oceans have been warming faster than climate models have predicted. Moreover, climate models that reach 90 years into the future do not tell the end of the story. There are feedback effects that can continue to increase the temperature long after CO2 emissions are controlled. These would include release of CO2 from the oceans and loss of polar ice that presently reflects sunlight rather than absorbing it. There are other feedback effects that may moderate the temperature (such as increased cloud formation). However, the net effect appears to be continued warming.

Things get much worse if we continue using fossil fuels as we do now. By the end of this century the CO2 concentration in the atmosphere will be about 1000 ppm. The last time the concentration was that high (approximately 40 million years ago) the earth was roughly 28°F warmer than it is now (even though the sun was about 0.4% less bright). (Source: J. Keil Science, Vol. 331 pp. 158-159.) The warming is greater at the poles than at the equator, but imagine your summers 15°F warmer than they are now. During this time period, it is estimated that the temperature of the tropical oceans was 107°F.

There is also evidence that dramatic changes in climate have occurred suddenly in the past - in periods of time as short as a decade or two. Such changes may be the result of sudden changes in ocean currents. Such risks are not factored into the climate change models that predict slow change over decades. (Click here for a list of relevant papers from the Woods Hole Oceanographic Institution.)

Global warming is not the only consequence of high CO2 concentrations in the atmosphere. For example, CO2 is an acid. It is clearly possible, though by no means certain, that acidification of the ocean will extinguish coral reefs, globally, within a few decades. (Sources: J.E.N. Vernon. Coral Reefs Vol. 27 pp. 459-472. Pandolfi et al. Science Vol. 333 pp. 418-422.)

It is well established that the elevated CO2 concentrations will persist for thousands of years after human production of CO2 ceases, and that climate consequences will persist even longer. (Geophysics Research Letters, 40, 5480, 2013)
People who deny that human production of greenhouse gasses is responsible for global warming often talk about the idea that global warming could be due to changes in cloud cover caused by changes in the intensity of galactic cosmic rays striking the earth. This proposal isn't as kooky as "galactic cosmic rays" sounds. The real problem is that we measure their intensity, and there is no evidence that the intensity of galactic cosmic rays has changed over the last century.

Step 2 -- Evaluate the Evidence

There isn't any obvious reason for being in favor of of global warming. (You can still click here for a list of consequences.) The reasons for trying to reduce global warming are obvious. The whole point to this article is to make it clear that global warming is real and a consequence of human activity - mainly burning fossil fuels.

Step 3 -- List the Options

An adequate discussion of the options for controlling global warming is beyond the scope of this article. However, the following information maybe helpful.

The European Union has set a target of limiting the global temperature rise to 3.6°F compared to levels before the Industrial Age. 1.6°F of this rise has already taken place. Limiting the temperature rise to 3.6°F requires limiting atmospheric CO2 to approximately 450 ppm. An influential paper by Pacala and Socolow (Science,Vol. 305 pp 968-972) suggests that atmospheric CO2 could be stabilized at around 450 ppm by implementing at least seven of the following 15 technological changes.

-more efficient vehicles − increase fuel economy from 30 to 60 mpg for 2 billion vehicles,
-reduce use of vehicles − improve urban design to reduce miles driven from 10,000 to 5,000 miles per year for 2 billion vehicles,
-efficient buildings − reduce energy consumption by 25%,
-improve efficiency of coal plants from today's 40% to 60%,
-replace 1,400 gigawatts of coal power plants with natural gas,
-capture and store carbon emitted from 800 GW of new coal plants,
-capture and reuse hydrogen created by the carbon capture above,
-capture and store carbon from coal to synthetic fuels conversion at 30 million barrels per day,
-displace 700 GW of coal power with nuclear,
-add 2 million 1 MW wind turbines (50 times current capacity),
-displace 700 GW of coal with 2,000 GW (peak) solar power (700 times current capacity),
-produce hydrogen fuel from 4 million 1 MW wind turbines,
-use biomass to make fuel to displace oil (100 times current capacity),
-stop de-forestation and re-establish 300 million hectares of new tree plantations,
-conservation tillage − apply to all crop land (10 times current usage).

However, as the CO2 concentration has already passed 400 ppm, it seems unlikely we will succeed in limiting it to 450 ppm. The Stern Report commissioned by the government of Great Britain evaluated costs of limiting CO2 to 550 ppm by 2050. This would require reducing CO2 emissions to about 75% of 2007 emissions. The estimated cost of achieving this reduction is 2% of gross world product (i.e. 2% of all the money spent for any purpose anywhere in the world). This comes to about $1.4 trillion per year worldwide. That is an enormous sum. The only reason for spending it is that doing nothing is estimated to cost between 5% and 20% of the gross world product long before the end of this century, and even greater sums later. The longer the delay, the greater the cost to the gross world product.

Step 4 - Prioritize

This comes down to the question of whether or not we are willing to sacrifice 20% of our grandchildren's income to save 2% of our own. Take your choice. Never mind the other consequences of global warming

Source