Category: Climate science

A physicist speaks: Dessler on climate sensitivity – very unlikely to be less than 2ºC

[youtube http://www.youtube.com/watch?v=mdoln7hGZYk&w=480]

There’s been much ado about climate sensitivity — the amount of warming we expect for a doubling of CO2 in the atmosphere — in the last month or two. A couple of recent papers, and an expected slight adjustment to the likely range in the upcoming IPCC fifth report ((From 2ºC to 4.5ºC in AR4 to 1.5ºC to 4.5ºC in AR5, with the most likely value still around 3ºC)), has led to speculation that we might have less to worry about, or more time to get emissions cuts in place. It would be great if it were true, but it isn’t. In this excellent short video, Andrew Dessler, professor of atmospheric sciences at Texas A&M university, explains why atmospheric physics means it’s very unlikely that the climate sensitivity can be below 2ºC.

For lots of other reasons why the most likely value remains about 3ºC, see this Skeptical Science post.

New Zealand’s changing climate and oceans: new Gluckman report out today

The Prime Minister’s science advisor, Sir Peter Gluckman, today released a new report looking at the probable impacts of climate change in New Zealand over the next 40 years. The report, New Zealand’s Changing Climate and Oceans: The impact of human activity
and implications for the future (pdf) is:

… intended to update the public on current scientific understandings of climate change and ocean acidification. In particular, it focuses on how these changes are likely to affect New Zealand’s climate and industries at a regional level over coming years.

The timing of the report — which appears at first glance to offer a reasonable overview of our current understanding of likely local climate changes — seems a trifle odd. In a matter of months the IPCC will release the first part of its Fifth Report, covering the underlying science, and while we’ll have to wait until March next year for the Working Group 2 report on regional impacts, Gluckman and his team would have had a firmer foundation for their report with only a modest delay.

I’ll be reading the report carefully over the next few days, and will have more to say in due course. I’m particularly interested in exploring how Gluckman approaches the risks associated with local climate changes, and his take on how the wider international context will impact New Zealand.

See also: Peter Griffin, NZ Herald.

Sea level rise and the Canterbury coastline

What are the prospects for the shorelines of Pegasus Bay as sea level rises, river flows change, and wave directions change? Someone who really knows her erosion from accretion is Sonny Whitelaw, the Hurunui Council’s biodiversity ambassador ((And SF author, writer, photojournalist, and Hot Topic reader.)). She’ll be talking to the Food For Thought Hurunui group on Monday night at the Memorial Library in Amberley, kicking off at 7-30pm. This is a presentation that Sonny has already given to the Waimakariri and Hurunui Councils, and comes highly recommended — especially if you live in or near a Canterbury coastal community.

Arctic sea ice time bomb ticking: the bang’s gonna be huge

Arctic2013July14Reading this press release about a new paper in Palaeogeography, Palaeoclimatology, Palaeoecology spoiled my day. It might not be obvious to a casual reader just glancing through the morning news — but a couple of paragraphs leapt out at me:

Atmospheric carbon dioxide concentrations recently reached 400 parts per million for the first time since the Pliocene Epoch, three million years ago. During this era, Arctic surface temperatures were 15-20 degrees Celsius warmer than today’s surface temperatures.

Ballantyne’s findings suggest that much of the surface warming likely was due to ice-free conditions in the Arctic. That finding matches estimates of land temperatures in the Arctic during the same time. This suggests that atmospheric carbon dioxide concentrations of 400 ppm may be sufficient to greatly reduce the spatial extent and seasonal persistence of Arctic sea ice.

In other words, losing Arctic sea ice brings huge warming to the lands around the Arctic Ocean. This is extremely bad news for a number of reasons:

Continue reading “Arctic sea ice time bomb ticking: the bang’s gonna be huge”

Arctic summer 2013: fragile ice pack feeling the pressure

Arctic2013July14

Looking down on the North Pole from satellite, NASA’s Arctic mosaic image for July 14 shows an unusually cloud-free view of the sea ice covering the Arctic Ocean. Click on the image to see the bigger original, and to zoom in on interesting regions. So far this year the sea ice melt has lagged behind last year’s record-setting performance, but in the last few weeks the rate of melt has increased significantly and the two years are moving closer together.

Arcticextent2013July13

The NSIDC’s sea ice extent graph (above, for July 13) clearly shows the increase in melt, but there is still a substantial gap — over 0.5 million km2 — between the two years. This is, however, the time of year when the melt season goes into overdrive, with sunshine pouring energy into the Arctic 24 hours a day.

Continue reading “Arctic summer 2013: fragile ice pack feeling the pressure”