Decreasing cloud volume increases global warming during the dinosaur period

According to a new study, about 100 million years ago, in the period of the dinosaurs, the warming of the air significantly reduced the amount of clouds, causing the temperature to rise.

The average tropical temperature during the Cretaceous period exceeds 100 ^° F (38 ^° C) and in the polar region is 50 ^° F (10 ^° C). Even palm trees can grow in Canada.

Scientists estimate greenhouse gas CO ₂ in the atmosphere is four times higher than today. According to Lee Kump, geologist at Pennsylvania State University 'Although CO2 is quite high, it is not enough to make the temperature so high as in the data obtained.' Presented in Science, Kump and his colleague David Pollard suggest that the decrease in cloud cover increases the temperature.

Scientists are now interested in global warming in ancient times because the process of accumulating greenhouse gases in this phenomenon is similar to what would happen if humans burn off fossil fuel reserves.' We are bringing the atmosphere into a state that it has not experienced for 50 million years .'

Kump and Pollard argue that the decrease in cloud cover in the Cretaceous period is derived from a decrease in cloud condensing nuclei, ie very small molecules that droplets are formed around. Today about half of such kernels are human-induced contaminants. In the Cretaceous, the molecules originate mainly from plants.

According to some climate models, global warming in the Cretaceous restricts plant growth. This is especially true for oceans, because in a warm water environment, algae will lose nutrients. If these patterns are correct, this also means that molecular material in the atmosphere comes from plants and seaweed drops. Less molecular material means less reflective clouds.'So the clouds are not as bright as they are today.'

Less brightness means less solar energy reflected back into space . This reflection is called the albedo effect. Starting from that hypothesis, Kump and Pollard put many reduced cases into a weather pattern to determine if this was the main cause of warming in the Cretaceous period.

In addition to the reduced brightness, they also found that the reduced molecule led to larger droplets . Because water droplets fall into rain when they reach a certain size, this reduces the amount of cloud cover. The most plausible model for this warming is when cloud cover decreases from 64% of the atmosphere to 55%.

Kump adds this system as a positive feedback loop. Warmer leads to less biological productivity, which reduces the amount of cloud cover and the temperature is even higher.'There is a lot of potential for global warming in this round of feedback.'

Meinrat Andreae is a biochemist at the Max Planck Institute of Chemistry in Mainz, Germany. He wrote an article published last year in Science, estimating the concentration of pre-human cloud condensation on land and sea. It was the article that caused Kump and Pollard to assume that the amount of reduced molecule led to lower albedo and thus exacerbated warming.

Andreae argued that although the biological production process reacts with warming, it still needs to be considered but the assumption that Kump and Pollard put forward is reliable.'This system is quite sensitive to the type that changes the molecular concentration at a natural level in the environment that is supposed to exist at that time.'

But the projections of this project about future warming are not convincing. In addition to CO2, humans also emit into the atmosphere other contaminants such as aerosol molecules (aerosols).

Kump noted that weather patterns suggest that warming over the past 30 years will become more serious 'without the presence of spray sprays in the atmosphere.'

Nowadays, thanks to environmental laws such as the Clean Air Act, the spray of pollutants are decreasing and leaving little coverage to global warming. So scientists need to decide whether biological production is actually reduced when the buildup of greenhouse gases is higher.

Kump said, 'If there is a missed feedback loop that we can prove is very important in establishing the ancient weather patterns, I think we need to focus on the model. That's right away. '