You mentioned Downton Abbey, which started filming right around when the volcano in Iceland was erupting. So in the first bits of film they did, they had a period sky to shoot in -- no contrails, no aircraft, only clouds and few of them. All of the flights had been grounded for safety. Maggie Smith told the cast that this was the kind of sky they would have seen back in 1910. Not many people remember a sky before there were jets and contrails, but we see a little bit of the environmental change every day.
Contrails, or condensation trails, or chemtrails lol, are in fact one of the things humans do which warm the planet. Just a little, but it's measurable. In the upper atmosphere, ice condensation nuclei are rare, so adding a source of water vapor up there makes a big difference into whether clouds form or not. And high, ice crystal clouds are mostly transparent to visible light, but absorb strongly in the infrared. In the aftermath of the September 11th attacks, we actually did notice a decrease in temperature over the U.S. related to change in the radiation balance, because there were no planes in the sky over half the continent.
We're closer to the ice age part of the cycle than the warm part, if you look at the Pleistocene history from ice and ocean cores. But the solar constant has been pretty constant lately, despite a brief dip in sunlight in the 60s. The 1940s were also cold, presumably due to stuff blowing up, adding aerosols while then going on to not use energy. There was some brief discussion about a new ice age starting into the 1970s, which is always one of those embarrassing moments for the field.
One of the new ice age theories which is particularly fascinating has to deal with the Gulf Stream. The Gulf Stream transfers a large amount of heat northward, and is largely responsible for the U.K. not feeling like Siberia. As detailed in the first five minutes of the "film" The Day After Tomorrow, before it completely goes off the rails, the decrease in North Atlantic salinity from glacial meltwater shuts down the thermohaline circulation that powers the Gulf Stream. And the thing is, it actually happened before. The pulse of fresh water from Lake Ojibway and Lake Agassiz is the most probable cause of a temporary cooldown for 300 years. Anyway that movie was super-fun to watch with my mesoscale meteorology class.
I don't think the thermohaline shutdown would happen again now, because the radiative forcing is just too large. Which is my way of saying that despite any possible events like Greenland sliding into the sea, I feel like the thermo part would prove larger than the haline part.
-- ∇×V
Contrails, or condensation trails, or chemtrails lol, are in fact one of the things humans do which warm the planet. Just a little, but it's measurable. In the upper atmosphere, ice condensation nuclei are rare, so adding a source of water vapor up there makes a big difference into whether clouds form or not. And high, ice crystal clouds are mostly transparent to visible light, but absorb strongly in the infrared. In the aftermath of the September 11th attacks, we actually did notice a decrease in temperature over the U.S. related to change in the radiation balance, because there were no planes in the sky over half the continent.
We're closer to the ice age part of the cycle than the warm part, if you look at the Pleistocene history from ice and ocean cores. But the solar constant has been pretty constant lately, despite a brief dip in sunlight in the 60s. The 1940s were also cold, presumably due to stuff blowing up, adding aerosols while then going on to not use energy. There was some brief discussion about a new ice age starting into the 1970s, which is always one of those embarrassing moments for the field.
One of the new ice age theories which is particularly fascinating has to deal with the Gulf Stream. The Gulf Stream transfers a large amount of heat northward, and is largely responsible for the U.K. not feeling like Siberia. As detailed in the first five minutes of the "film" The Day After Tomorrow, before it completely goes off the rails, the decrease in North Atlantic salinity from glacial meltwater shuts down the thermohaline circulation that powers the Gulf Stream. And the thing is, it actually happened before. The pulse of fresh water from Lake Ojibway and Lake Agassiz is the most probable cause of a temporary cooldown for 300 years. Anyway that movie was super-fun to watch with my mesoscale meteorology class.
I don't think the thermohaline shutdown would happen again now, because the radiative forcing is just too large. Which is my way of saying that despite any possible events like Greenland sliding into the sea, I feel like the thermo part would prove larger than the haline part.
-- ∇×V