Tyson starts on Venus. Venus is about 30% closer to the Sun than we are, and extremely, ridiculously hot. When the Soviets sent Venera 13 in 1982 to Venus' surface, it lasted about two hours, long enough to take some pictures and send them home via radio waves, and then the thing was fried.
All the way to Venus. For this picture.
An average of about 900 degrees Fahrenheit. Imagine more than twice the temperature you bake a potato in. Clouds of sulphuric acid and carbon dioxide shield the planet from the Sun's light- very little of it actually gets through. So, despite Venus' location, clouds obstructing the sun's light (and therefore, heat energy) should keep the planet quite cold. I mean, that's what happens during a volcanic, or nuclear winter. Why doesn't that happen on Venus?
Ever been in a greenhouse? Light streams in the windows, hits surfaces and plants. The plants convert the light energy to sugars and starches they need, but other surfaces, especially the floor, will absorb leftover light, and re-radiate it back out as heat. Now, close the windows at the top. Heat will rise due to convection to the top of the greenhouse and.... stay there. Because the glass acts as a barrier to slow the heat from escaping. That's why people use them in winter, and vent the fuck out of them in summer. There are several gasses that mimic this: water vapor, methane, ozone, and... carbon dioxide. Which Venus has a shitload of.
Venus' atmosphere is about 96% carbon dioxide. Compare that to Earth's atmosphere, which is about .04% carbon dioxide. So, yes, limited light gets to the surface of Venus. Once that light strikes the surface, its energy is absorbed by the planet, converted to heat, and radiated back out into the sky. Smart people call it "radiative forcing". Instead of ultimately re-radiating back out into space, the carbon dioxide of Venus' sucks it up. Which means that all of that heat stays on Venus, turning it into a sauna.
So, why does Earth have so little CO2 in its atmosphere? Life. We have living creatures, plants and algae, that love carbon dioxide. They absorb it, turn it into whatever they need for survival, (remember that episode?) and exhale whatever is left. For plants, that is oxygen, which we turn around right back into CO2. When the plants die, they decompose underground, turning CO2 into deposits of coal, petroleum, or natural gases (Remember?) For algae, it's sediments, usually as limestone or coral, that are then deposited on ocean floors. The deposits eventually become coral reefs, or an ocean floor. Tectonic activity can actually pressure these deposits into huge formations above ground, like the White Cliffs of Dover on Britain's East Coast.
In other words, the Earth has ways of storing carbon dioxide, so it stays out of the atmosphere, keeping our carbon dioxide levels low, around 3 molecules of CO2 for every 10,000 other molecules of gasses in the atmosphere. This creates a great Goldilocks zone for us: we have enough that we warm up, but not so much that we get too hot. We always re-radiate out a significant percentage of the Sun's warmth back into space, like a greenhouse with the top windows open. In other words, we avoid Venus' fate. Or do we?
According to NOAA, the National Oceanic and Atmospheric Association, in the mid-1800s, when the Industrial Revolution started with coal, we had a concentration of 285 molecules of CO2 for every 1 million molecules in the atmosphere. Since then, we've burned even more coal, as even more of our lives became dependent on using it for electricity. Add petroleum turned to gasoline for cars and trucks, and then additional natural gas as a substitute for coal. Now, do that for about 160 years. All that carbon dioxide, stored as fossil fuels, is now released back into the atmosphere. It took millions of year to store. But only about 160 years to release. Our concentration now, as of 2013, was about 395 molecules of CO2 for 1 million molecules. It's estimated that we haven't had this much CO2 in our atmosphere for 800,000 years.
Wait, how do we know that? Like Clair Patterson (remember?), we go to Antarctica. Instead of looking for lead, we look for carbon dioxide. And we find it. When snow falls on the continent, it doesn't melt. It stays frozen, and gets compacted by the next snowfall, which also traps gasses between the snow layers. These layers, over time, form ice sheets. By drilling into the ice sheet, and taking out cores, we can find the gas pockets and analyze them. As you go down through successive layers, that like going back in time. The deeper we drill, the father back in time we go. By plotting concentrations of gasses over layers of ice sheets, we can see trends over time. And while the CO2 level has varied over 800,000 years, it has undoubtedly gone up dramatically since the Industrial Revolution and the burning of fossil fuels began.
Okay, just so we get it:
This is CO2 concentrations since the mid-1700s:
Source: EPA
This is global temps since the 1880s:
From NASA/Goddard Space Institute
Just for shits and giggles, these are estimated CO2 levels over the last 400,000 fucking years:
Combined Ice Core records + Mauna Loa observations
In other words, there's a whole shitload of extra CO2 up there. Are we sure we did it?
Yes, we're sure. Like, 99.9% sure. How are we sure it wasn't.... say.... volcanoes? They still erupt here, and they do spew a ton of crap with it's own chemical signature, distinct from the chemical signatures of fossil fuel emissions. By isolating the chemical signatures, we can compare emissions. Volcanoes are estimated to spew 200-500 million tons of carbon dioxide a year. Us? We dump about 30 billion tons of carbon dioxide. About every year. In other words, we spew about 60-150 times as much carbon dioxide into the air as volcanoes. Every. Fucking. Year. And, unlike volcanoes, our emissions have fewer and fewer smokestacks belching out sun-blocking particles. So, we don't produce a temporary fossil-fuel winter before our warming. We warm up right away.
Is it the Sun? It seems the likeliest culprit. After all, the Sun started this whole mess in the first place sending photons of light our way. Notice, this hypothesis doesn't address the extra amount of CO2 in the atmosphere at all. It just acknowledges that we're getting warmer but not because of CO2. But scientists don't buy it. The Sun has an 11-year cycle, in which, yes, there's some temperature variation. But 11-year cycles of warmer/cooler don't explain a steady, 130 year climb up.
Scientists have been pointing out the consequences of increasing CO2 levels since 1896, when Svante Arrhenius estimated that doubling then-CO2 levels would cause polar ice to melt.
It's a real page turner
In 1938, Guy Callendar became the first scientist to demonstrate that worldwide temperatures were rising.
Carl Sagan wrote about in in 1980s Cosmos. It's been the subject of government hearings. Articles. Reports by every government, including the United Nations. Over and over again, we've been told to expect temps to change if we keep dumping CO2 in the atmosphere. And yet, we keep doing it. With no end in sight.Tyson also spends a little time demonstrating why climate can be studied and modeled, when weather can only be predicted a day or so in advance. Weather, he shows, is like a dog that you're walking on a leash. The dog's unpredictable movements are weather variations. But the dog's path, tracked over time, follows a pattern marked by the person walking the dog. Climate is really the study of past weather variations over huge timescales, which gives us patterns. Patterns we can use to model future climate.
Yes, weather is blue and climate is hot pink
Tyson spends no time on the denial-of-climate-change industry. So, neither will I. But you can go look for yourself. He also spends very little time on the consequences of increasing heat, except on one of the worst consequences: melting permafrost, which is basically frozen bog. Up in Alaska, there's a ton of basically frozen compost, with a ton of trapped methane. Go back to the beginning of the recap. Notice methane mentioned anywhere? Yep, it too is a greenhouse gas. It traps ridiculously more heat than CO2. Which means that releasing it from melted permafrost is like that scene from Ferris Bueller's Day Off when Cameron kicks the car repeatedly, and the car crashes into a ravine below.
Instead, Tyson wants to talk solutions. Notably, solar power, which Augustin Mouchot debuted at Paris' 1878 World Expo. He wowed the crowds, and the judges, by making ice from concentrating the sun's power and running a motor with it. In 1913, Frank Shuman demonstrated the first solar power station in Maadi, Egypt. It was originally to provide sorely-needed irrigation in deserts, but WW1 put the kabosh on it. Also deadly to solar power: the cheapness of gas and coal. Or at least, they seem cheap. Until we get the real bill. Tyson also briefly mentions wind power. It can be offshore, saving land, and doesn't require sunlight.
So, what's holding us back? Tyson reminds us that we have the know-how to solve our problems. What we don't have is the will. Tyson ends by comparing our need to develop fuels that don't ruin our climate with our conversion of the rockets necessary for launching nuclear warheads into the science of getting people to the Moon. Getting to the moon took about eight years. It was a massive project that launched us into Space, and taught us that we could learn so much more than what's on the Moon. Tyson ends by letting JFK inspire us with his declaration of landing on the Moon by the end of the 1960s, as we pan out on a city of the future, covered in roof gardens.
Because it is hard
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