Tag Archives: sea ice melt

Climate Change Feeds Hurricane Sandy

By Robert Cooper, published on Monday 29 October 2012 by Science 2.0

Hurricane Sandy, 2012: Massive and dangerous Hurricane Sandy has grown to record size as it barrels northeastwards along the North Carolina coast. – Jeff Masters, Weather Underground, Oct. 28 2012.

Science paper, 2010: Fewer but fiercer and more-destructive hurricanes will sweep the Atlantic Basin in the 21st century as climate change continues, a new modeling study by U.S. government researchers suggests. commentary by Richard Kerr on Bender, M.A. et al., 2010. Science, 327(5964), pp.454–458.

Hurricane Sandy, 2012: If ‘Frankenstorm’ pans out to be as powerful and odd as the models currently forecast, then it may be said that this storm will be unique in the annals of American weather history. Christopher Burt, Weather Underground, Oct. 26, 2012.

Report by the National Research Council, 2010: The destructive energy of Atlantic hurricanes is likely to increase in this century as sea surface temperature rises – “America’s Climate Choices: Adapting to the Impacts of Climate Change”, National Research Council, National Academies of Sciences, 2010.

Where I sit in New Jersey, we are preparing for a direct hit from a record-setting hurricane. We all know that no one event can be blamed on climate change. But this freak storm certainly seems to match the warnings we’ve gotten over the past decade. Let’s consider what exactly makes Hurricane Sandy so “freak”, and whether this freakiness may be a harbinger of the new normal.

There are at least three factors making Hurricane Sandy such a threat:

1. Warm sea surface temperatures

Global warming has been raising sea surface temperatures around the world. The water off New England set record highs this year, meaning that Sandy will have more energy to feed from than usual as she churns North.

Sandy will draw energy from the abnormally warm ocean just off the Atlantic coast. Note this is in Celsius. The water off NJ is about 5°F higher than average, and set record highs in 2012. Source: NOAA National Hurricane Center.

Yes, there are natural variations that affect sea surface temperatures, in particular the Atlantic Multidecadal Oscillation. But consider the plot below showing North Atlantic temperature changes from normal. The ~60 year oscillation is clear, but so too is the fact that each peak is stronger than the one before.

North Atlantic sea surface temperature anomalies (°C). Source: Wang, C.&Dong, S., 2010. Geophys. Res. Lett, 37, p.L08707.

2. A “blocking pattern” shoving the storm back on shore

A blocking pattern is essentially when the jet stream gets kinked. The current kink is pushing Sandy back on shore where most hurricanes would keep veering out to sea. A recent analysis showed that blocking patterns like this are more likely thanks to a warming Arctic. As Arctic sea ice keeps melting to new record lows, the darker water absorbs more heat, which it later releases to the atmosphere. The effect of all this is a weaker jet stream more prone to kinking.

3. A merger with a winter storm

Ok, so actually, this one’s not climate related. Ok, so prediction: rising temperatures will give hurricanes warmer oceans to feed from, and more moisture to dump on us, making them more destructive. Observation: we are about to get walloped by what looks to be a history-making storm. Prediction: ocean temperatures will keep rising and blocking patterns will become more frequent. Observation: Hurricane Sandy is feeding off of record ocean temperatures and a kinked jet stream.

Now, it is certainly true that we still don’t completely understand hurricanes. It is true that models are not perfect. It is true that Hurricane Sandy could have happened even without climate change. It is true that climate change doesn’t “cause” an event, just like doping alone won’t win you the Tour de France. And, as always, it is true that we should not draw conclusions from a single event.

So then, is Hurricane Sandy just a freak event, or is she an instructive example of what we should expect more often?  Let’s look at a paper just published in PNAS, which put together a long-term data set of hurricane activity based on storm surges. That means this is not a model – it is empirical evidence from the past 90 years.

We observe that [hurricane activity is greater in] warm years… than cold years and that the relative difference… is greatest for the most extreme events. -Grinsted, A., Moore, J.C.&Jevrejeva, S., 2012. Proceedings of the National Academy of Sciences.

Climate change is happening, this is why we care.

What Sea-Ice Melt Means For Our Climate Policy – By David Spratt

Originally published in newmatilda.com

There’s half as much sea-ice as there was 30 years ago and the annual summer melt keeps smashing records. David Spratt on why Australian policy-makers should be paying attention.

In the last few days something so dramatic has happened in the Arctic that it demands another look at Australia’s climate policies.

On Friday 24 August, annual summer melting of the floating sea-ice in the Arctic Ocean smashed the previous record, with another three weeks of the melt season still to to go. Scientists are calling it “stunning” and “astounding”. This breaks the record set in 2007. Back then there were scientific gasps that the sea ice was melting “100 years ahead of schedule”.

Thirty years ago, the summer sea-ice extent was around 7.5 million square kilometres (similar to the area of Australia), but this year it will end up at half that figure. And the ice is becoming thinner, due to melting from below by warmer seas, and the relentless loss of thicker, multi-year ice. So the volume of the summer ice will in 2012 be only around one quarter of what it was three decades ago. Now it looks like the sea-ice will be gone in summer within a decade or so, maybe sooner. That’s what many of the cryosphere scientists and models are saying.

Climate Commissioner Will Steffen commented on the ice melt in yesterday’s newspapers: ”We can expect to see an ice-free Arctic at about the middle of this century”. This line looks out of touch with the most recent data and, in my humble opinion, is a case of scientific reticence. In 2007, NASA climate science chief James Hansen proposed in a research paper: “I suggest that ‘scientific reticence’, in some cases, hinders communication with the public about dangers of global warming. If I am right, it is important that policy-makers recognise the potential influence of this phenomenon.”

The enormity of the present situation is best summed up by sea-ice blogger Neven:

“Basically, I’m at a loss for words, and not just because my jaw has dropped and won’t go back up as long as I’m looking at the graphs. I’m also at a loss — and I have already said it a couple of times this year — because I just don’t know what to expect any longer. I had a very steep learning curve in the past two years. We all did. But it feels as if everything I’ve learned has become obsolete.”

What is also stunning are sea-ice daily extent figures of ice loss averaging more than 100,000 square kilometres per day for the last four days. This suggests melt is accelerating very late in the melt season in a pattern that has never before been observed. The Arctic this year is heading into new territory and it looks like 2012 may in retrospect be seen as the year when a new melt regime took hold.

Climate change impacts are frequently happening more quickly and at lower levels of global warming than scientists expected, even a decade or two ago. And this week the Arctic has provided a dramatic and deeply disturbing example.

The sea-ice decline is being relentlessly driven by positive reinforcing feedbacks. As the ice area reduces, reflective ice is replaced by dark seas which absorb most of the sun’s radiation. As the seas warm, more ice is lost and the seas warm more.

The ice is now much thinner on average than in the past, as the extent of multi-year ice declines sharply. Thin ice is easily smashed up by storms and rough seas, and that is what happened this year. In early August, a huge Arctic ocean storm decimated the sea ice area which was melting out at a record rate, before the high waves and winds shattered the Siberian side of the ice cap. But there have been subsequent, less well-reported, cyclonic storms churning up the ice, which may explain why the melt rate has not eased off in the last 10 days.

With Greenland passing its previous record melt on 8 August 2012 — with more than a month of the melt season left — it seems to be an extraordinary year, but the record show it may be the new norm as the Arctic warms at two-to-four times the global average, and increasing areas of exposed sea are absorbing vast amounts of energy that would previously been reflected by ice.

So what does all this mean for the rest of the world, and for Australia?

Consequences include:

• Devastating impacts on the communities and species of the Arctic north.

• Changes to atmospheric patterns and the jet stream in the northern hemisphere, affecting the frequency of extreme weather events; both the extreme winters Europe has experienced in recent years, and the recent prolonged heatwave, drought and wildfires in the USA, are examples of what can happen. Scientists are now just beginning to understand (pdf) how these profound Arctic shifts may be increasing the likelihood of more persistent and extreme weather.

• Increased heat in the Arctic pushing up the rate of melt on the Greenland ice sheet, and sea levels.

• Melting of Arctic permafrost with dramatic consequences. In an interview with Bloomberg on 16 August, NASA’s top climate scientist, James Hansen said the increasing sea-ice melt may be a harbinger of greater changes such as the release of methane compounds from frozen soils that could exacerbate warming, and thaw of the Greenland ice sheet: “Our greatest concern is that loss of Arctic sea ice creates a grave threat of passing two other tipping points — the potential instability of the Greenland ice sheet and methane hydrates… These latter two tipping points would have consequences that are practically irreversible on time scales of relevance to humanity.

For Australian policy-makers, two issues stand out.

Firstly, adaptation and sea-levels. Sea level planning in Australia is based on a possible 1.1 metre rise by 2100. But this does not include any allowance for accelerated ice mass loss from Greenland and Antarctica. The City of Boston (see chart) is now considering sea-level rise scenarios of up to two metres, and prudent risk assessment procedures suggests Australia should do the same. Professor Tim Lenton, the world’s leading authority on climate tipping points says,  “the (Arctic) system has passed a tipping point”. More worrying, he says, and very likely, is the collapse of the Greenland ice sheet that could cause catastrophic sea-level rise.

Chart: Projected sea-level rise to 2100 (inches). Source City of Boston.

The gap between science (the necessary scale of action to reclaim a safe climate) and politics (what is politically “possible”) is growing alarmingly wide. Experts like James Hansen warn that the emissions reduction targets of both major parties in Australia would result in a lot more than two degrees of global warming and are a recipe for global disaster. There is a forlorn hope amongst the political class that two degrees of warming won’t be as bad as the science suggests. On recent trends — where observations such as in the Arctic often exceed the scientific projections for rates of change — it’s likely to be worse.Secondly, emissions reduction targets. The bi-partisan political orthodoxy in Australia is that to reduce greenhouse emissions by 5 per cent by 2020 is doing enough. Few voices are prepared to point out that buying international permits means emissions will actually go up, rather than down, by 2020, or that the planned expansion of Australia coal exports will make us a bigger exporter of fossil fuel carbon by 2030 than Saudi Arabia.

The gap between science (the necessary scale of action to reclaim a safe climate) and politics (what is politically “possible”) is growing alarmingly wide. Experts like James Hansen warn that the emissions reduction targets of both major parties in Australia would result in a lot more than two degrees of global warming and are a recipe for global disaster. There is a forlorn hope amongst the political class that two degrees of warming won’t be as bad as the science suggests. On recent trends — where observations such as in the Arctic often exceed the scientific projections for rates of change — it’s likely to be worse.