Action plans aren't always the greenest

Here is a simple question: How should we measure the success of climate policy?

The answer should be, “By maximizing CO2 reduction for every dollar spent.”

This smart approach is standard practice for many private companies. Both Microsoft and Amazon spend on projects that are the fastest and most effective at reducing their impact on the climate.

For example, a government subsidy for rooftop solar in cloudy Western Washington costs about $200 to reduce one metric ton of CO2. Projects that capture methane at landfills cost less than $10 to gain the same benefit – 20 times more effective.

When...