Cosmic rays – again

Crab Nebula

There’s been a spate of articles claiming that a new CERN/CLOUD project paper shows that cosmic rays are the real cause of climate change:

A major scientific study is casting fresh doubt on the theory of man-made climate change. In fact, this latest research shows it may be something far beyond the control of humans.

Research by the prestigious European Organization of Nuclear Research supports the theory that periods of earth warming are caused by solar activity and so-called cosmic rays, rather than by human activity.

The findings of the landmark study, dubbed CLOUD, are rocking climate science.

Landmark study indeed! Continue reading Cosmic rays – again

Climate clippings 42

Climate sensitivity

James Wright at Skeptical Science has constructed a summary of some recent work done by James Hansen and colleagues. Climate sensitivity is the temperature change caused by a doubling of CO2. In this post I referred to a paper by Hansen et al, Earth’s energy imbalance and implications. Wright is working from a paper by Hansen and Sato entitled Paleoclimate implications for human-made climate change which contains much of the same material, including Table 1 on p16.

The bottom line goes like this:

The exact value of climate sensitivity depends on which feedbacks you include, the climate state you start with, and what timescale you’re interested in. While the Earth has ice sheets the total climate sensitivity to CO2 is up to 8°C: 1.2°C direct warming, 1.8°C from fast feedbacks, 1°C from greenhouse gas feedbacks, and nearly 4°C from ice albedo feedbacks. The slow feedbacks have historically occurred over centuries to millennia, but could become significant this century. Including CO2 itself as a feedback would make climate sensitivity even higher, except for the weathering feedback which operates on a geologic timescale. (Emphasis mine)

CO2 alone, not CO2e, of 450ppm is likely to give us an ice-free planet – eventually.

I take it that the stability we’ve had during the Holocene is unusual. Upset the balance with a bit of the trace gas CO2 and the system can go wild. Continue reading Climate clippings 42