Paleoclimate modeling has shown that climate change, which today is associated with emissions of greenhouse gases, “canceled” natural global cooling, reported in the journal Scientific Data. As shown by the scale analysis in the mid-19th century the Earth’s average temperature was 0.7 degrees below the peak six and a half thousand years ago, when the Earth began to cool, however, over the past decade it has increased one degree Celsius — which is a lot for such a short period of time.
It is known that in the late Holocene after the peak warming began a gradual cooling that lasted until the middle of the last century, and then the average temperature of the Earth began to grow rapidly. Many researchers such a sharp transition to warm at least a partial contribution of greenhouse gases that humanity emits into the atmosphere. However, in order to draw conclusions about what the contributions of natural processes and some human activity, and more accurately predict what to expect in the future, it is necessary to build a high-quality reconstruction of paleoclimate.
Darrell Kaufman (Darrell Kaufman) from Northern Arizona University, along with colleagues applied five different statistical methods for reconstructing global average surface temperatures over the last 12,000 years. They relied on a database of paleoclimate, which was published a few months ago. 93 researchers from 23 countries analyzed evidence, including lacustrine deposits, sediments, peat and ice, which could be useful in order to draw conclusions about past temperature changes. In the end, they managed to create a database that includes 1319 images collected from 679 plots around the world.
Group Kaufman modeled the climate of the past, and then compared the models with average temperatures in the 19th and 20th century, to trace how the industrial revolution could affect her.
As expected, 12 thousand years ago the Earth’s average temperature was much lower than in the 19th century. However, over the next several millennia, it has grown steadily and eventually exceeded baseline level. The peak values it reached about 6500 years ago, then the atmosphere gradually began to cool (by about 0.1 degree Celsius per thousand years). In the words of the researchers, this cooling could be related to the slow cyclescaused by changes in earth’s orbit, causing the amount of sunlight received by the Northern hemisphere of the planet diminished, and the result was the little ice age of recent centuries.