Why urgent? There's no stop button. There's no emergency brake.
notes: expanded excerpts from "Why it's Urgent:"
"There's no "STOP" button. There's no emergency brake. Think of our climate system as an enormous tanker with a world's worth of momentum behind it. Once it gets going, it can't turn around on a dime. We can't just wait until the point that climate change becomes unbearable to decide we want it to stop. The pollution that causes climate change stays in the atmosphere for hundreds of years. Even if we stopped emitting pollution today, we would continue to experience warming for a considerable time. Put another way, there's a big time lag between when we emit pollution and when we feel its full effects.
"Beware of the vicious cycle: The warmer it gets, the worse it gets. Pollution from our burning of dirty energy causes warming. This warming is setting in motion a series of self-reinforcing cycles that are contributing to even more warming. For example:
Permafrost (frozen soil) has historically been a store for the heat-trapping gases that contribute to global warming. As permafrost thaws, these gases are released.
Oceans are also a store for heat-trapping gases. As the oceans warm, however, gases are released into the atmosphere. Ever notice that a lot more gas is released when you open a bottle of Coke when it's warm rather than cold? The same goes for oceans.
Arctic ice acts like a bright white shield – it reflects sunlight back into space and helps keep earth cool. When it melts, the deep blue ocean it reveals absorbs sunlight, accelerating warming.
Do the math. Scientists have repeatedly told us that global temperature rise above 2°C is a "prescription for disaster". Bill McKibben recently outlined the math: We can only burn about 565 more gigatons of carbon by mid-century to keep to this limit. On our current path, the door to the 2°C limit is closing fast."