Climate Change Primer

The Problem

At its essence, the climate change argument is simple and irrefutable: as humans burn fuels, we emit the products of the combustion reaction into the atmosphere. We learn in high school chemistry that a combustion reaction emits CO₂:

C_iH_jO_k + (−k/2 + i + j/4)O_2(g) → iCO_2(g) + j/2 H₂O_(g)


As we burn increasing amounts of fuel, we are making changes to our environment on an unprecedented level. Measurements of the level of atmospheric greenhouse gases (GHG) since 1000 AD are well known, an example is shown in the figure to the left. Since the industrial revolution, the levels of GHG in our atmosphere have been exponentially increasing along with our fuel consumption.

While it is clear that we are impacting our climate on an enormous scale, the consequences are not all known or universally accepted; the global warming debate is much more complicated than the climate change debate. Global mean temperature records in figure 2 show a striking correlation–increasing temperatures over the same period of increasing GHG concentrations, though including a dip in temperatures in the 1970’s due to global cooling from particulate emissions. The temperature increase of about 1°C over the last 100 years may not sound like much, but only about 8°C separates the hottest recorded years in history with the depths of the coldest ice ages.

Global temperatures fluctuate periodically, and the next figure shows that the correlation between GHG concentrations and temperatures holds remarkably well for the last 400,000 years. The figure also shows that the earth is now hotter than it has been for the last 100,000 years and near the hottest temperatures recorded on earth for the last 400,000 years. Current greenhouse gas concentrations are higher than ever recorded, with methane, a particularly important greenhouse gas,at more than twice its record high.

The climate models cannot explain the recorded temperatures without including the effects of human activity, as shown in the next figure.

Atmospheric concentrations of GHG are integrals of the amount we emit, which is projected to grow exponentially for the near future. Global temperatures take some time to adjust to atmospheric GHG levels, so even if all GHG emissions stopped today, the planet would continue to feel the effect of past emissions for the lifetime of the GHGs in the atmosphere, hundreds to thousands of years.
The vital questions are: 1) as we continue to emit GHGs, what are the effects to our climate? 2) How can we adapt to or mitigate the consequences of projected increasing GHG emissions?

Consequences

There are the known knowns, the known unknowns,and the unknown unknowns. Some consequences of GHG concentrations are known: gases in the atmosphere absorb energy radiated from the earth, trapping some heat in the earth. Warmer ocean surfaces result in more severe tropical storms. A warmer climate leads to expanding deserts but longer growing seasons. Melting glaciers raise global water levels. As glaciers melt, methane clathrates trapped in glacial ice are released into the atmosphere, further increasing GHG concentrations.
Some consequences of GHG concentrations are known to have an effect on the environment, but it is not known if the feedback loop is positive (reinforcing the trend of warming) or negative (pushing back, and cooling the climate). Examples include clouds: warming increases evaporation and thus cloudiness; it is not known whether clouds will increase temperatures by blocking in heat (water vapor is also a GHG) or decrease temperatures by increasing albedo.
The unintended and unknown consequences of climate change could potentially become the worst. Until several years ago, the major heat flows around the world were not understood, and the importance of the slowing of the vital Thermohaline Circulation was not understood. We now know that this ocean current keeps Northern Europe 20 °C warmer than other locations at the same latitude, and as a warming earth shuts down the THC, Northern Europe may quickly resemble Newfoundland. Before literally watching a glacial ice shelf melt in weeks in 2002, we didn't understand how quickly the ice could melt.
A prudent policy would take into consideration major threats due to climate change. What are the consequences of a Katrina every decade or every year? If global sea levels rise quickly, major population centers will be displaced and buildings will be lost.

Economical Solutions

Conservation can be effective and easy. For example, we could reduce the "vampire load" (so called because it sucks you dry at night) which comes from plugged in electrical devices on standby such as TVs and phone chargers and accounts for about 10% of the US electricity consumption. The US policy on auto emissions, which account for 25% of GHG emissions, is reprehensible, as even China is due to pass tougher standards by 2008. As shown in the next figure, increasing automobile power and weight have offset gains in engine efficiency to lower fuel efficiency of new cars sold in the US since 1980.

Market-based solutions such as cap-and-trade systems or taxes on negative externalities have solved similar problems. To deal with acid rain, a cap-and-trade system was implemented for SO_x and NO_x emissions at less than one quarter the projected cost.
Increased funding for research may lead to the much talked about "technological fix.'' Rather than lag behind, if the US takes the lead on global initiatives on GHG emissions, we can create incentives for R&D to solve major problems in the field, and US firms can become leaders in the industry. If we continue to elect leaders who not only drop the ball but kick it farther away, we will fall further behind in important future industries, just as US car makers fell behind Japanese firms as fuel efficiency became more of a factor in the last several years.