When I was a kid (in the 50s and 60s), people talked about Earth cooling rather than warming so much so that when I first heard about Global Warming causing Climate change I was confused as I wondered what had happened to those predictions of a looming Ice Age.
The climate changes in response to some external change or forcing. These forcings include changes in the intensity of the sun’s radiation, volcanic eruptions, rapid releases of greenhouse gases, and changes in Earth’s orbit.
The biggest climate changes in the past 800,000 years have been the ice-age cycles. These ice-age cycles are the result of slow changes in Earth’s orbit which alter the way the Sun’s energy is distributed on the Earth’s surface as a function of latitude and season.
Interestingly; in the absence of human-caused global warming, Earth’s current orbital changes would actually be cooling the planet. A 2009 study in the journal Science, “Recent Warming Reverses Long-Term Arctic Cooling,” found that prior to approximately 1900, the Arctic had been slowly cooling for some 2000 years, which was replaced by rapid warming only in the last century or so, driven by carbon pollution.
In the last 35 years of global warming, the sun and the climate have been going in opposite directions with the sun actually showing a slight cooling trend.
Carbon dioxide levels in the air have now passed 400 parts per million (ppm). The last time the Earth’s atmosphere was at 400 ppm of CO 2 was a few million years ago, long before Homo sapiens roamed the Earth. Back then, the climate was 2°C (3.6°F) to 3°C (5.4°F) above preindustrial temperatures, and sea level was some 15–25 meters (50–80 feet) above modern levels.
The world’s top scientists are confident that humans are responsible for so much of the warming because most of the naturally occurring forcings that affect global temperature would tend to be cooling the Earth rather than warming it.
To be perfectly clear: in the absence of human activity, the planet would likely have cooled in recent decades.
The sun’s level of activity tends to have a modest, cyclical impact on global temperatures but we have seen “the deepest solar minimum in nearly a century.
Volcanic activity in recent decades has released particles that partially block the sun and also serve to cool the planet slightly.
Finally, the underlying long-term temperature trend for the Earth as a function of changes in our orbit has been a very slow cooling.
Human activity has overwhelmed all of these trends and completely ended any speculations about a possible future ice age any time soon.
If facts don’t work, you can always try humor: click for the Dragon Theory of Climate Change