24 August 2014

Dangerous climate change: Myths and reality (3)

Third in a 3-part series | Part 1 | Part 2

by David Spratt

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Myth 6: Long-term feedbacks are not materially relevant for carbon budgeting

Some elements of the climate system respond quickly to temperature change, including the amount of water vapour in the air and hence level of cloud cover, sea-level changes due to ocean temperature change, and the extent of sea-ice that floats on the ocean in the polar regions. These changes amplify (increase) the temperature change and are known as short-term or “fast” feedbacks.

There are also long-term or “slow” feedbacks, which generally take much longer (centuries to thousands of years) to occur. These include changes in large, polar, land-based ice sheets, changes in the carbon cycle (changed efficiency of carbon sinks such as permafrost and methane clathrate stores, as well as biosphere stores such as peat lands and forests), and changes in vegetation coverage and reflectivity (albedo).

23 August 2014

Dangerous climate change: Myths and reality (2)

Second in a 3-part series | Part 1 | Part 3

by David Spratt

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Myth 3: Big tipping points are unlikely before 2°C

Tipping points, often an expression of non-linear events, are difficult to project. But if it is sometimes hard to see tipping points coming, it is also too late to be wise after the fact. Estimated tipping points around or below ~1.5ÂșC include: 
  • West Antarctic Ice Sheet: Current conditions affecting the West Antarctic Ice Sheet are sufficient to drive between 1.2 and 4 metres of sea rise, and these glaciers are now in "unstoppable" meltdown at global average warming of just 0.8ÂșC (NASA, 2014A; Rignot, Mouginot et al., 2014; Joughin, Smith et al., 2014). 

22 August 2014

Dangerous climate change: Myths and reality (1)

First in a 3-part series | Part 2 | Part 3

by David Spratt

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Few would disagree that the world should avoid "dangerous" (or unsafe) climate warming, but what does that term mean? What does climate safety mean? Is climate change already dangerous? Are greenhouse gas levels already too high? This report surveys some recent developments in climate science knowledge as a way of discerning the gaps between myth and reality in climate policy-making.

Scientific and political reticence

Amongst advocates for substantial action on climate warming, there is a presumption of agreement on the core climate science knowledge that underlies policy-making, even though differences exist in campaign strategy.

But the boundaries between science and politics have become blurred in framing both the problem and the solutions. Amongst advocates, advisors and policy-makers there are very different levels of understandings of the core climate science knowledge, how it is changing, what constitutes "danger", what needs to be done, and at what pace.