The Solutions We Have and the Breakthroughs We Need

By Bill Gates

Intro

• 52 billion is how many tons of greenhouse gases the world typically adds to the atmosphere every year (may go up or down but generally increasing). Zero is what we need to aim for.
• Virtually every activity in modern life - growing things, making things, getting around from place to place - involves releasing greenhouse gases
• The world needs to provide more energy so the poorest can thrive, but we need to provide that energy without releasing any more greenhouse gases

Why Zero?

• Greenhouse gases trap heat, causing the average surface temperature of the earth to go up. The more gases there are, the more the temperature rises. And once greenhouse gases are in the atmosphere, they stay there for a very long time; something like one-fifth of the carbon dioxide emitted today will still be there in 10,000 years.
• In climate terms, a change of just a few degrees is a big deal. During the last ice age, the average temperature was just 6 degrees Celsius lower than it is today. During the age of the dinosaurs, when the average temperature was perhaps 4 degrees Celsius higher than today, there were crocodiles living above the Arctic Circle.
• Why are some places heating up more than others? In the interior of some continents, the soil is drier, which means the land can’t cool off as much as it did in the past.
• A gas like methane is much worse than carbon dioxide. It drives the temperature up immediately, and by quite a bit. When you use carbon dioxide equivalents, you aren’t fully accounting for this important short-term effect.
• How do greenhouse gases cause warming? The short answer: They absorb heat and trap it in the atmosphere. They work the same way a greenhouse works - hence the name.
• All molecules vibrate; the faster they vibrate, the hotter they are. When certain types of molecules are hit with radiation at certain wavelengths, they block the radiation, soak up its energy, and vibrate faster.
• The earth radiates some of the energy back toward space, and some of this energy is emitted in just the right range of wavelengths to get absorbed by greenhouse gases. Rather than going out harmlessly into the void, it hits the greenhouse molecules and makes them vibrate faster, heating up the atmosphere.
• Only molecules made up of different atoms, the way carbon dioxide and methane are, have the right structure to absorb radiation and start heating up.
• By the end of the century, soils in the southwestern United States will have 10 percent to 20 percent less moisture, and the risk of drought there will go up by at least 20 percent.
• California is a dramatic example of what’s going on. Wildfires now occur there five times more often than in the 1970s, largely because the fire season is getting longer and the forests there now contain much more dry wood that’s likely to burn. According to the U.S. government, half of this increase is due to climate change.
• According to research cited by the IPOC, a rise of 2 degrees Celsius would cut the geographic range of vertebrates by 8 percent, plants by 16 percent, and insects by 18 percent.
• If the temperature rises by 2 degrees Celsius, coral reefs could vanish completely, destroying a major source of seafood for more than a billion people.