For the entire history of our species, humans have lived on a planet capped by a chunk of ice at each pole.
For the entire history of our species, humans have lived on a planet capped by a chunk of ice at each pole. But Earth has been ice-free for about 75 percent of the time since complex life first appeared. This variation in background climate, between partly glaciated and ice-free, has puzzled geologists for decades.
Now a team of scientists led by UC Santa Barbara’s Francis Macdonaldhas published a study suggesting that tectonic activity may be the culprit. They found that long-term trends in Earth’s climate are set by the presence or absence of collisions between volcanic arcs and continents in the tropics. The results appear in the journal Science.
“There’ve been a few hypotheses but no agreements as to why we have warmer or colder climates on these very long timescales,” said Macdonald, a professor in the Department of Earth Science.
And when Macdonald says “long timescales,” he’s talking about 10 million-year periods, at a minimum. These are broad climatic trends, the backdrop against which natural and human-made fluctuations play out. Scientists have a relatively good understanding of what factors influence the climate on a thousand-year timescale, according to Macdonald.
Read more at UC Santa Barbara
Photo Credit: PATRICK KELLEY CC BY 2.0 , ANAND OSURI CC BY-SA 4.0