Climate Change 101
The Earth is Warming
We know Earth is warming from surface temperature stations and satellites which measure the temperature of the Earth’s surface and lower atmosphere. We also have tools which measure the warming of the Earth’s oceans. Satellites have measured an energy imbalance at the top of the Earth’s atmosphere. Glaciers, sea ice, and ice sheets are all receding. Sea levels are rising. Spring is arriving sooner each year. Measurements of the energy-content of the world’s ocean show an enormous increase over the last 50 years.
The warming is continuing: The 2000s were hotter than the 1990s, which were hotter than the 1980s, which were hotter than the 1970s. The warming remains, and in fact is easier to see, after we filter out the short-term effects of the sun, volcanoes, and El Niño cycles.
Humans are increasing greenhouse gases and greenhouse gases cause warming
We can verify that humans emit greenhouse gases in different ways:
- Accounting: We’re emitting about 30 billion tons of CO2 per year, and the amount in the atmosphere is increasing by about 15 billion tons per year. Our emissions have to go somewhere – half goes into the atmosphere, while the other half is absorbed by the oceans (which is causing another major problem – ocean acidification).
- The carbon in fossil fuels has a different isotopic composition than carbon from other sources, which allows us to confirm that the extra carbon in our atmosphere comes from burned fossil fuels. Other supporting lines of evidence are shown in the picture below.
We can verify that greenhouse gases cause warming through various methods in thermodynamics and atmospheric chemistry. This is the hardest aspect of the subject for non-scientists to understand. We know how the chemical components of the atmosphere absorb and radiate energy, and satellite measurements demonstrate that the Earth is radiating less energy than it used to at the wavelengths absorbed by carbon dioxide, which means that carbon dioxide is responsible for holding in the extra heat. This view is supported by surface measurements showing that more radiation at those wavelengths is returning to Earth. There are other lines of evidence as well. See here for more.
The Consequences Are Likely to Be Bad
The likely consequences for human activities will be complex, but on balance, they will probably hurt more than help. The main difficulties will be heat waves, draught, floods, water management problems, agricultural problems, biodiversity loss, and consequent economic difficulties. There are also possibilities for even greater difficulties, such as the disruption of the world carbon cycle, so that carbon builds up more quickly than it’s building up now. See here for a summary of some of the likely positives and negative outcomes of climate change.
Smart Risk Management Means Taking Action
Most of us are conservative when it comes to risk management. We buy insurance for our homes even though the risk of serious damage is low. We would rather be safe than sorry.
Arguably, there’s no more important object than the global climate. We rely on the climate for our basic requirements, like food and water. Prudent risk management in this case is clear. The scientific evidence discussed above demonstrates a risk of harmful climate change. There are uncertainties as to how harmful the consequences will be, but uncertainty is not a reason for inaction. There’s high uncertainty whether you’ll ever be in a car accident, but it would be foolish not to prepare for that possibility by purchasing car insurance. Moreover, uncertainty cuts both ways, and it’s as likely that the consequences will be worse than we expect as it is that the consequences won’t be very bad.
The above presents only a small taste of climate research. There is much more to it than we can present here. Many of us are unaware of how much work has been done on the subject and how much we know about it. We encourage those interested in the subject to study it further. Here are good places to start:
- Skeptical Science (website)
- Real Climate (website)
- The Rough Guide to Climate Change (book)
- The Climate Crisis: An Introductory Guide (book)