HIGHER LEVELS OF CARBON DIOXIDE FOLLOWED HOTTER TEMPERATURES
The Mid-Cretaceous era was the heyday of the dinosaurs but was also the warmest period in the last 149 million years, with temperatures in the tropics as high as 35 degrees Celsius and sea levels 170 metres higher than today. Even during months of darkness, swampy temperate rain forests were able to grow close to the South Pole, revealing an even warmer climate than what had previously been expected.
To get these conditions, scientists believe that 90 million years ago the Antarctic continent was covered with vibrant and dense vegetation and there were no land-ice masses on the scale of an ice sheet. The work also suggests
that the carbon dioxide (CO2) levels then were higher than expected during the mid-Cretaceous period, 115-80 million years ago, challenging the previous climate models for that period.
“Before our study, the general assumption was that the global carbon dioxide concentration in the Cretaceous was roughly 1,000 parts per million (ppm),” according to geoscientist Torsten Bickert from the University of Bremen in Germany. “But in our model-based experiments, it took carbon dioxide concentration levels of up to 1,680 ppm to reach the average temperatures back then in the Antarctic.”
However, little was known about the environment south of the Antarctic Circle at this time. Now, researchers have discovered evidence of a temperate rain forest in the region, such as would be found in New Zealand today. This was despite a four-month polar night, meaning for a third of every year there was no life-giving sunlight at all.
The evidence for the Antarctic forest comes from a core of sediment drilled into the seabed near the Pine Island and Thwaites glaciers in West Antarctica. One section of the core, that would have originally been deposited on land, caught the researchers’ attention with its strange colour. The presence of the forest suggests average temperatures would have made it unlikely there would be an ice cap at the South Pole at that time.
The team CT-scanned the section of the core and discovered a dense network of fossil roots, which was so well preserved that they could make out individual cell structures. The sample also contained countless traces of pollen and spores from plants, including the first remnants of flowering plants ever found at these high Antarctic latitudes.
To reconstruct the environment of this preserved forest, the team assessed the climatic conditions under which the plants’ modern descendants live, as well as analysing temperature and precipitation indicators within the sample. The team of British and German scientists examined forest soil from the Cretaceous period within 559 miles of the South Pole and analyzed the preserved roots, pollen and spores within the soil.
They found that the annual mean air temperature was roughly two degrees warmer than the mean temperature in Germany today. Average summer temperatures were around 19 degrees Celsius; water temperatures in the rivers and swamps reached up to 20 degrees; and the amount and intensity of rainfall in West Antarctica were similar to those in today’s Wales. The current warmth of the earth is not unprecedented, not just by this new ice core evidence of an ancient rain forest in the Antarctic but also the Medieval Warming Period which was two degrees warmer than the global temperature today.
The Little Ice Age (LIA), which occurred approximately 450 tears ago, and the Medieval Warm Period (MWP) were both discovered and proven by Ice Core evidence back before 1990, but despite all the evidence presented they were removed from all IPCC reports after Michael Mann submitted his hockey stick graph (tree ring proxy data) which showed the earth had been actually cooling for 1000 years. Fellow scientist Keith Briffa also submitted a graph which actually showed cooling after 1961 but was rejected because it didn’t fit the narrative. The period known as the Medieval Climatic Optimum. China was, however, cold at this time (mainly in winter) but South Japan was warm (Yoshino, 1978). This period of widespread warmth is notable in that there is no evidence that it was accompanied by an increase of greenhouse gases.
Cooler episodes have been associated with glacial advances in alpine regions of the world, such neo-glacial’ episodes have been increasingly common in the last few thousand years.
Of particular interest is the most recent cold event, the Little Ice Age, which resulted in extensive glacial advances in almost all alpine regions of the world between 150 and 450 years ago (Grove, 1988) so that glaciers were more extensive 100-200 years ago than known early everywhere (Figure 7 2) Although not a period of continuously cold climate, the Little Ice Age was probably the coolest and most globally extensive cool period since the Younger Dryas