Around 1.2 million years ago, a shift in global climate began that caused a change in the timing of the alternating warm and cold periods—called interglacials and glacials—that have persisted during the Pleistocene Ice Age. Prior to that time, ice age glacial periods lasted about 40,000 years but since ~700,000 years ago ice-age cycles have lasted for around 100,000 years. Orbital variations, called the Croll-Milankovitch cycles, do exert some forcing on the 100,000 year time scale, but it is relatively weak. Orbital cycles seem to many too feeble an explanation for the change in glacial-interglacial timing. Some scientists have attempted to attribute the timing shift to a drop in CO2 but a new study confirms that carbon dioxide levels were not the cause of the climate shift.
It is no surprise to anyone who has studied the history of our planet and the life it harbors that CO2 levels have been falling for billions of years. Despite all the hoopla over rising CO2 levels, eventually Earth will have lost so much carbon dioxide from its atmosphere that plants and trees will suffocate, signaling an end to life as we know it. Now, a team of scientists from the California Institute of Technology, led by physicist King-Fai Li, have proposed a way to avert disaster—get rid of much of the atmosphere.
One of the fundamental aspects of Earth's ecological and climate systems is the way carbon moves through the biosphere. From land to air to water, through living organisms and even the plant's crust, carbon—the stuff of life—is always on the move. Scientists thought they had a pretty good understanding of how the carbon cycle works, until now. Recent work with strange, jellyfish like creatures called thaliaceans is causing scientists to re-evaluate the workings of the carbon cycle.
NASA researchers report that much of the atmospheric warming observed in the Arctic since 1976 may be due to changes in tiny airborne particles called aerosols. Though greenhouse gases are invariably blamed for global climate change, and the shrinking Arctic ice cover in particular, this new research indicates that as much as half the warming in the Arctic can be attributed to sort lived particulate pollution—basically soot. Unlike the dreaded gas, CO2, aerosols do not stay in the atmosphere very long, suggesting that the effects of any warming caused by aerosols would quickly be reversed if their emissions ceased.