“A Brief History of the Earth’s Climate” by Steven Earle, PhD

It took me a long time to make my way through this book and I'm not sure a lot of it sunk in. (Pretty sure this is a me problem and not a problem with the book itself.) The main impression I came away with is that, as Steven Novella is fond of saying about everything, "it's complicated." Whereas the previous climate book I read made everything simple and easy to understand (possibly overly so), this book really dug into the details. 

Earle explains that many things have an impact on the earth's climate: 

1. The Sun is getting hotter. This certainly serves to warm the climate, but it has been happening very slowly, over an immense timeframe (billions of years). There are also shorter-term solar variations (sunspots) but their effects on the climate have been minimal. 

2. Continental drift has caused changes in albedo (which is basically how "reflective" the earth is, which in turn has an effect on global temperatures.

3. Volcanoes release greenhouse gases, but the overall effect of a typical volcanic eruption is actually cooling of the climate due to release of sulphur dioxide (which converts to sulphuric acid or sulphate aerosols, which can remain in the atmosphere for months to years, blocking the sun).

4. Milanković cycles (variations in the Earth's orbit and tilt) also affect the climate, but these changes occur over thousands (or hundreds of thousands) of years. 

5. Ocean currents are important for redistribution of warmth around the world, and disruptions in these currents are both an indication that climate change is occurring, and a cause of greater temperature extremes (hot areas get hotter and cold areas get colder). The El Niño Southern Oscillation causes short-term increases and decreases in global temperatures, but they don't explain the recent continuous upward trend over time. 

6. Comets or asteroids hitting the earth have caused climate changes and extinctions in the past (and could do so again some day). Some organisms die from the impact, many more from the following radiative heat and resulting wildfires, and even more from the persistent clouds of soot that could cause a few years of darkness, then several more years of cold and dry conditions, followed by acid rain, then extended warming as a result of all the greenhouse gases caused by the fires. 

Bottom line; many factors impact the earth's climate. But there is one factor that has had a more precipitous impact in the shortest period of time: the human being and its related activities. None of the 6 issues listed above can explain the current trend of global warming (think hockey stick graph, which starts with normal climate variations but quickly switches to an incredibly steep rise in atmospheric greenhouse gases due to industrialization). Furthermore, based on ice core records, the Earth should actually be in a cooling trend, but it is certainly not. 

The last chapter of this book was my favorite: what can I personally do about climate change? That's what I've been trying to figure out for years. The recommendations of this book fell squarely between Greta Thunberg-style sacrifices (don't eat meat or dairy, don't buy new things, and don't fly) and those of the Green New Deal (individuals can't have an impact--it's up to governments). Earle gave a lot of suggestions (if not overly-specific ones):

• Decrease consumption of beef (dairy too, to a lesser extent)
• Walk, bike, or take a bus more. Drive and fly less. Get an electric car next time you buy one.
• Lobby your government and power company to generate cleaner electricity. 
• Get photovoltaic solar panels. 
• Set your thermostat lower in winter and higher in summer. 
• Wash clothes in cold water (and not every single time you wear them)
• Only run the dishwasher when it's full
• Take shorter showers.
• Waste less food, and compost what is unavoidably wasted
• Recycle.
• Don't replace your phone or computer as often (due to high "embodied emissions"--in other words, these things take a lot of energy to make).

I'd thought I would probably get rid of this book after reading it, but I came to the opinion that it is a good reference. I doubt I would ever read it all the way through again, but it will be useful if I ever have a question about a particular aspect it covers--I can just re-read that chapter.

Full disclosure: I wrote this blog post on an airplane. Fail!