If climate changes naturally over time, why isn the current warming just another natural cycle?
Previous major global-scale changes in climate, the ice ages, were a product of orbital changes that occur over thousands of years, not tens of years as the current warming has. Shorter-scale changes, such as the “Little Ice Age,” have been linked to changes in solar output. Neither orbit variation nor solar output changes can explain the current warming, so it’s very likely that greenhouse gases are the culprit. The industrial activities that our modern civilization depends upon have raised atmospheric concentrations of carbon dioxide and methane to higher levels than at any point during the last 650,000 years.
Earth’s climate does change naturally, but the current warming is not natural. Known natural causes of warming, such as the sun, have been constant in the past 30 years, so they cannot explain the warming of the past 30 years. The pattern of the current warming is also highly unnatural. For example, it is warming more at night than during the day; this is expected for CO2-caused heat trapping, because CO2 works at night, whereas natural warming would be more in the day. A long list of similar patterns (a “fingerprint” of human-caused warming) proves conclusively that the warming isn’t natural.
