It doesn’t require much imagination to see that our planet is warming. Just look at the increasing series of climatic anomalies that have occurred over recent years. Have you recently experienced any unseasonably strange or unexpected weather patterns in your home town?
What warms the Earth?
In essence, there are only three factors that can affect the earth’s temperature and thereby be responsible for global warming:
1. Activity of the sun
2. The reflectivity of the earth
3. Greenhouse gases
The sun is the ultimate climate controller: hotter sun means warmer Earth. Interestingly, however, since about 1985 the sun has changed in ways that, if anything, should have cooled the planet—even as global temperatures have been rising.
Around 30% of the sun’s energy that reaches the Earth is reflected back into space. Changes in the balance between sun absorption and sun reflection can affect global temperatures. Over time, two types of human activity (human-produced pollution and human land use) collectively have actually had a cooling effect on the climate: increasing earth’s reflectivity through increases in polluting reflective sulfur-containing particles, and by brightening the planet through increases in forest clearing for agriculture since 1750. Warming resumed after 1975 when industrialized countries began to clean up their particulate pollution while continuing to increase their greenhouse gas emissions. These data suggest that reflectivity is not causing global warming.
It is well known that carbon dioxide traps heat in the earth’s atmosphere, and that burning fossil fuels releases carbon dioxide (CO2). Continued burning of coal and oil increases concentrations of CO2 in the earth’s atmosphere, making the planet warmer. This is called the greenhouse effect, and is the only remaining rational explanation for the rise in global temperatures in recent decades. There are direct measurements of CO2 concentrations in the atmosphere going back more than 50 years, and indirect measurements (from ice cores) going back hundreds of thousands of years. These measurements confirm that concentrations are rising rapidly.
Natural amounts of CO2 in the atmosphere vary, with evidence (owing to the unique signature of the chemical composition of the CO2) that additional CO2 comes mainly from coal and oil. Today’s CO2 levels are at an alarming 30% more than the highest natural levels over the past 800,000 years, with increased CO2 levels contributing to periods of higher average temperatures throughout that long period of time.
These data make an almost indisputable case for the idea that human activity is causing the earth to get warmer, primarily through the burning of fossil fuels, with a smaller contribution from deforestation. All other rational scientific explanations have been eliminated. Check it out.