Guy McPherson and the end of humanity (not)

Is climate change going to wipe out humanity over the next 10 years? Prof Jim Renwick doesn’t think so…

Ecologist Guy McPherson has been touring New Zealand for the past couple of weeks, explaining why humanity has only 10 years to live (a kind-of Ziggy message that has immediate appeal to me). After his appearance on the Paul Henry breakfast show, I was called by TV3/Newshub for comment. Based on my understanding of climate change science I said that though the situation is very serious — dire even — extinction in 10 years is not going to happen. When I gave my remarks to Newshub, I knew little about McPherson but I understood that he is a very knowledgeable biologist who should not be dismissed lightly.

So, what’s the story? Is McPherson right? Is the IPCC woefully conservative and keeping the truth from us all? I had the opportunity to hear Prof McPherson speak in Paraparaumu on Saturday (Dec 10th) to get more insight into what his views really are. It was a very interesting presentation, and a very interesting discussion with the audience of 50-odd Kāpiti coasters who showed up to hear him. As the old saying goes, extraordinary claims require extraordinary evidence. What we heard was extraordinary for sure, but was not too convincing in terms of evidence.

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Antarctic sea ice: The end of the trend?

west antarctic sea iceUnusual things are happening to Antarctic sea ice extent. We are about a month away from the traditional time of maximum extent (around 20 September), and each year for the last six years, total sea ice extent around the Antarctic has been above normal. The last three years have been record-breaking, with 2014 seeing the 20 million square kilometre threshold exceeded for the first time since satellite records began in 1979 (Figure 1). But this year, sea ice growth stalled in early August and is currently going nowhere. For the first winter since 2008, total Antarctic sea ice extent is below normal (Figure 2).

ASIExtentanom201409 Figure 1: September Antarctic sea ice extent, percent difference from the 1981-2010 normal.

Antarcticseaice20150819 Figure 2: Antarctic sea ice extent in 2015 (blue line). The dashed line shows 2014 extent, the gray line the 1981-2010 average extent and the shading represents the two standard deviation spread about the average.

What’s more, the pattern of sea ice change this winter is the opposite of the trend pattern we’ve seen over the past few decades towards more ice around the Ross Sea and less ice near the Antarctic Peninsula1. This year, near the Antarctic Peninsula, we have more ice than normal, and less than normal north of the Ross Sea and across parts of the Indian Ocean (Figure 3). A real turn-around.

ASI20150816extentmap Figure3: Antarctic sea ice coverage for 16 August 2015 (white). The thin solid line shows the 1981-2010 average sea ice edge for this date.

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  1. Turner, J., J. C. Comiso, G. J. Marshall, T. A. Lachlan-Cope, T. Bracegirdle, T. Maksym, M. P. Meredith, Z. Wang, and A. Orr, 2009: Non-annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent. Geophys. Res. Lett., 36, L08502, doi:08510.01029/02009GL037524. []

A tale of two hemispheres

Jim RenwickAt the end of June, Professor Jim Renwick of Victoria University gave his inaugural lecture. As you might expect of a climate scientist, it concerns what we know about the climate system and where we’re heading. He pulls no punches. Jim has been kind enough to put together a text version of the lecture for Hot Topic: it follows. You can watch the full lecture, with accompanying slides, on the video embedded at the end of the post.

We live in a golden age of earth observation. With a few clicks of a mouse on a web browser, any of us can see the state of the global ocean surface, the current condition of the Greenland ice sheet, how much rain is falling in the tropics today, and on and on. Plus, the International Space Station (ISS), and a series of satellites such as MODIS give us wonderful images of our home planet. The climate science community can tell, with unprecedented coverage and timeliness, just what is going on in the climate system. It is a great time to be a climate researcher, but also a worrying time, in both cases because we can see exactly what is changing.

One thing the ISS pictures emphasise is just how thin the atmosphere is, a thin blue layer between the solid earth and the blackness of space. Not only is this life-supporting envelope very thin, some of the key gases in the atmosphere are there in only trace amounts, so we can change the properties of the atmosphere easily, by targeting the right gases. The discovery of the ozone hole 30 years ago brought this home with a bang. And we’ve found that build-up of carbon dioxide (CO2) in the atmosphere can have a profound effect on the climate system, right down to the bottom of the oceans.

Carbon dioxide is important because it’s a crucial control on the surface temperature of the earth. It is very good at absorbing heat (infrared radiation) welling up from the earth, then re-radiating both up and down, in the process warming the earth’s surface. The effect is very like a blanket put on a bed – what’s under the blanket warms up. More CO2 is like putting another blanket on the bed and less is like taking away a blanket. No CO2 and the earth freezes – temperatures like we had in the South Island in late June would be the norm everywhere, all the time. While there are several other “greenhouse gases”, carbon dioxide is the most important since it stays in the atmosphere so long, hundreds to thousands of years.
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Renwick on NZ’s 11% cut: follow us down the path to catastrophe

RenwickThis guest post is by Carbon News editor Adelia Hallett, published with permission.

New Zealand will face droughts, floods, fires, social upheaval and catastrophic global economic damage if the world follows the country’s lead on cutting greenhouse gas emissions, says one of our leading climate experts. Dr James Renwick – Professor of Physical Geography at Victoria University, an International Panel on Climate Change lead author, and formerly a principal scientist at the National Institute on Water and Atmosphere – says that cutting emissions at the rate that New Zealand proposes would lead to at least 3 degrees of warming by the end of the century.

That’s warmer than at any time in the history of human agriculture and settlement, which started around 10,000 years ago.

The Government announced on Tuesday that New Zealand would go to international climate change negotiations in Paris later this year with a post-2020 emissions reduction target (known as an Intended Nationally Determined Commitment, or INDC) of 30 per cent below 2005 levels by 2030. That’s the same as 11.2 per cent below 1990 levels. New Zealand also has a target of halving emissions on 1990 levels by 2050.
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Totten hots up, ice shelves melting: it’s grim down south

AntarcticaCryosat2Much news in recent weeks from Antarctica, and none of it good. An Argentinian base on the tip of the Antarctic Peninsula recently reported a new high temperature record for the continent — 17.5ºC. A team of scientists has discovered that East Antarctica’s Totten Glacier — which drains a catchment that contains enough ice to raise sea levels by 3.5 metres — is vulnerable to melting caused by warm ocean water lapping underneath the ice and reaching inland1. Another group has stitched together satellite data on ice shelf thickness gathered from 1994 to 2012 and found that the ice shelves — mostly stable at the beginning of the period, are now losing mass fast2. From the abstract:

Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 km3 per year for 1994-2003 to rapid loss of 310 ± 74 km3 per year for 2003-2012. West Antarctic losses increased by 70% in the last decade, and earlier volume gain by East Antarctic ice shelves ceased. In the Amundsen and Bellingshausen regions, some ice shelves have lost up to 18% of their thickness in less than two decades.

The Amundsen region is home to the Pine Island Glacier, notorious for its current rapid loss of mass, and probably already past the point of no return for long term total melt. The map below shows the big picture: large red dots are ice shelves losing mass. Blue dots are shelves gaining mass.

Antarcticiceshelves

Ice shelves are important features of the Antarctic cryosphere. They buttress the ice piled up on the land, slowing down the flow of ice into the ocean. As the shelves lose mass, the flow of ice from the centre of the continent can speed up, adding to sea level rise. There’s a very good overview of the process — and the findings of the Paulo et al paper — in this excellent Carbon Brief analysis.

The study of the Totten Glacier — one of the fastest thinning glaciers in East Antarctica — is the first to look at the detail of the sea floor and ice thickness in the area. The study finds that there are “tunnels” under the ice leading into a deep trough inland that cold convey warm water inland — the same process that has destabilised the Pine Island Glacier in West Antarctica. As the authors suggest, rather drily, “coastal processes in this area could have global consequences”.

These signs of rapid changes around the coasts of Antarctica, together with hints that large parts of the huge East Antarctic ice sheet are at risk of following West Antarctica into the sea, suggest that even if sea levels only rise by a metre by the end of this century as the IPCC projected last year, the longer term picture will be a great deal wetter than that. After all, there is the equivalent of 60 metres of sea level rise locked up in East Antarctica.

For a very good overview of the state of our understanding of what’s going on in Antarctica, I recommend a listen to VUW’s Professor Tim Naish being interviewed by Radio New Zealand National’s Kim Hill last Saturday. Naish even covers what’s happening to the sea ice down there, but a longer term study of the sea ice is getting under way, led by another VUW prof — Jim Renwick.

  1. Greenbaum JS et al, (2015), Ocean access to a cavity beneath Totten Glacier in East Antarctica, Nature Geoscience, doi:10.1038/ngeo2388 []
  2. Paolo, F.S. et al, (2015), Volume loss from Antarctic ice shelves is accelerating, Science, doi/10.1126/science.aaa0940 []