By far the largest human influence on the climate system, and the one nearly all climate policy has focused upon, is the emission of greenhouse gases. But the relationship between our emission of these gases and their influence is more complicated than you might imagine.

There’s nothing at all wrong with scientists as activists, but activism masquerading as The Science is pernicious.

Only once in the geological past—the Permian period, 300 million years ago—have atmospheric CO2 levels been as low as they are today. Plant and animal life flourished abundantly during times when CO2 levels were five or ten times higher than today’s. But those were different plants and animals. So while carbon dioxide, in and of itself, is not

Creating alarming headlines through highly uncertain projections of the future is one thing, but promoting the specter of climate-related deaths by distorting existing data is quite another.

There would surely be less support for, say, promoting renewable energy sources if they were more realistically portrayed as a possible way to mitigate a possible future problem instead of an essential solution to an imminent crisis.

The energy that flows in and out of the climate system is measured in watts per square meter (W/m2). The sunlight energy absorbed by the earth (and hence the heat energy radiated by the earth) amounts to an average of 239 W/m2. Since a 100-watt incandescent light bulb gives off, well, one hundred watts (almost all as heat), this means the planet

Particularly promising here is the use of information-based approaches to transportation (such as suggesting more efficient routes for a trip or better monitoring and control of engine performance) and building operations (such as turning down the heating or cooling in unoccupied rooms).

A third “easy” step toward reducing emissions is further research and development in emissions-lite technologies.

Climate data is readily available online from the US government, for example, from the EPA (at www.epa.gov/climate-indicators) and NOAA (at www.noaa.gov/climate