Homework 12 & 13: Sketch 4

If cities require new buildings to use 100% electric heat, will that raise or lower their greenhouse gas emissions?

Electric heating can cause a short-term rise in emissions in areas that get their electricity from fossil fuels. But without electric heat, we can’t get greenhouse gas emissions to zero

What is the ideal level of carbon dioxide in the atmosphere for human life?

Atmospheric CO₂ levels of between 280 and 350 parts per million created the climate that let humanity build and feed the modern world. The farther we get from those levels, the more we run the risk of disturbing that balance.

With low-carbon technologies improving so fast, does it sometimes make sense to wait to invest in new infrastructure?

It can make sense to wait for low-carbon technology to improve in efficiency and cost, but to slow climate change we must balance what makes economic sense with what reduces emissions the fastest.

Is there a danger that pumping liquid carbon dioxide underground could have the same negative impacts as fracking?

Pumping carbon dioxide deep underground can cause earthquakes under certain conditions, but there are ways to prevent this.

Which is more likely: electric airplanes or hydrogen-powered airplanes?

For long-range flights with many passengers, liquid fuels like hydrogen are probably our best bet.

What is “sustainability”? Is it the same thing as taking action on climate change?

Climate action is just one form of sustainability—a concept that asks us to see the big picture of what we are taking from the Earth, and how our actions affect future generations.

Is there a place in the atmosphere where carbon dioxide is concentrated, and if so, can we remove it?

Carbon dioxide mixes evenly through the atmosphere. But the atmosphere as a whole is densest near the ground, so a cubic foot of air at ground level will contain more carbon dioxide molecules than a cubic foot of air high up in the sky.

Why have I heard that eating meat is bad for the climate?

Meat directly produces greenhouse gas emissions and requires more land and other resources than plant-based foods.

How are countries held accountable under the Paris Agreement?

The short answer is that there is no hard enforcement in the Paris Agreement. But all the members regularly meet, share progress, and renew their pledges of climate action, encouraging every country to step up its commitments.

Why aren’t we looking at more hydropower?

Hydropower is already a major source of power globally—it’s the largest source of renewable electricity and one of the fastest growing—but there are limited places to build hydropower, and large dams carry a number of social and environmental concerns.