Plows, Plagues, & Petroleum: How Humans Took Control of Climate

[theclimateblog]

When we talk about anthropogenic global warming, we tend to be referring to the dramatic rise in greenhouse gases like carbon dioxide since the beginning of the Industrial era, some two hundred years ago. Scientists often refer to this apparent change in the atmosphere as the "Anthropocene," the beginning of significant human impact on the earth.

Comments

Re: Everyone needs to Frankenstein. Or Jurassic Park.

[theclimateblog]

Correlation is certainly not causation, but it's important to note that Ruddiman offers a hypothesis. If scientists are going to take the most parsimonious explanation, in order for Ruddiman's hypothesis to be refuted, we need data that disproves it. If you're going to offer an alternative hypothesis, it has to be more plausible (or simpler) than the one he's offering. I'm not saying I'd stake my life on it, but it's a fascinating and fun theory to explain anomalous rises in greenhouse gases before industrialization.

I'd be curious to hear what "thermodynamic" ideas support your non-anthropogenic theories, and how those predict ice ages in a more effective way than Milankovitch forcing. What are these "huge factors?" Why do you suppose that climatologists wouldn't have an appropriate handle on this problem?

In response to your point about the tropical planet: If we look at geological history, that's not the case. Aside from the "snowball earth" theory, you're overstating the warmth of previous epochs. Gondwanaland was glaciated during the Devonian (360mya), and permanent Antarctic ice has been around since about 15mya. Even so, this isn't the warmest time in Earth's history, for a number of reasons. Milankovitch oscillations have been happening for quite some time, but only in the last two million years have we had periodic ice ages. This is typically attributed to the gradual shift of the continents away from the equator after the breakup of Pangaea, coupled with the uplift of the Tibetan Plateau, the drying of the inland sea in North America, orographic uplift in the Sierras, Rockies, and Andes, the closing of the Isthmus of Panama, and the narrowing of the Drake Passage. These factors changed atmospheric and oceanic circulation sufficiently to cool the Atlantic enough to allow for glacial periods when the earth's tilt and orbit were conducive.

Enter the Industrial age - typical interglacials (like the one we're in) last about 10,000 years - and our last ice age ended about 12,000 years ago. The debate about whether we should "let" another ice age happen isn't even at stake here - what is of greatest concern is the impact of future warming, beyond current levels, on human health, security, the natural environment, and economies. Your statement about El Nino ignores the impacts of heavy rains and mudslides, droughts and associated wildfires, early frosts, late snowstorms, less winter snowpack, and other factors that have a marked effect on peoples' lives. Given the slow response of the earth system to change, even if we cut our emissions 100% today, we'd still warm the planet for another century because of the lagged thermal response of the oceans and atmosphere. Those "poor South American countries" stand to lose the most from warming, because they're already at their ecological and economic limitations in many ways, and have less of an ability to adapt than their first world counterparts.

I understand where you're coming from about scare tactics, but I certainly didn't get that impression from Ruddiman's book, to bring it back to the topic. I also believe there is a difference than basing action on fear, and basing it on urgency. Deciding how much and why the earth is warming is a scientific question, and I'm a scientist. Deciding what to do about it is a values-laden question that's best left to the policy folks. Scientists can make predictions and assess the damage as we go along, and urge action only in the areas they know. It's up to the public to decide what it values, and if those values are strong enough to warrant action.