New models still give Arctic summer ice 30 years

A thin sheet of sea ice reflects the rising sun off the east coast of Greenland on Apr. 14, 2012, with thicker sea ice and icebergs in the background. On average, the most up to date climate models that accurately simulate recent Arctic ice melting predict a nearly ice-free September by 2035. Credit: NASA/Jefferson Beck

Predictions from a collection of the latest climate models on average say that ice will be nearly gone from the Arctic by the 2030s. But when you don’t include man-made – or ‘anthropogenic’ – CO2 emissions’ ‘forcing’ effect, those models show a much icier picture.  “This clearly shows that if you don’t consider anthropogenic forcing, the ice won’t decline that fast,” said Muyin Wang from the University of Washington. “It should be oscillating around a much higher level.”

These findings echo some that Muyin and her Seattle colleague James Overland, from the US National Oceanic and Atmospheric Administration (NOAA) Pacific Marine Environmental Laboratory, made in 2009. Then, James and Muyin used climate models that formed the basis for the Intergovernmental Panel on Climate Change’s fourth assessment report, which was published in 2007. “Because of this report’s success a lot more modelling groups around the world started doing simulations,” Muyin told me. Scientists are now bringing their improved old models together with new ones in a project to compare them. Having found the old models bad at reproducing measured shrinkage of Arctic ice at the end of the 20^th century, James and Muyin wanted to see if the new and improved ones could do any better.

It’s important to be able to reproduce real data to be confident in models’ predictions, Muyin said. “If you are interviewing someone for a job, you look at their resumé, to see if they did a good job in the past,” she explained. “Then you know that they can do the job going forward. It’s a similar idea here, if models can simulate the past climate, then they’re the models we want to use in the projection.”

In a paper published in the scientific journal Geophysical Research Letters on Tuesday, they started from 32 different models, and compared them with satellite data on sea ice coverage. Overall, their resumés were slightly better than the older models: For the period from 1981-2005, the average of all these models was near the ice coverage actually seen, whereas the older models had overestimated the values.  But the highest and lowest estimates in both groups were still very similar.

Warming cost estimates cheat our children

Economic calculations saying future generations are at least as important as we are make a strong argument for replacing fossil fuel electricity generation with renewable energy sources like wind. Credit: Caveman Chuck Coker/Flickr

The financial benefits of reducing CO2 emissions, and avoiding the climate change they would bring, is at least 2.6 times larger than the US government estimates. And, according to Laurie Johnson of the Natural Resources Defense Council in Washington, DC, and Chris Hope at the University of Cambridge, UK, they could be much higher. Undervaluing the damages, which play a part in how the US government makes decisions about climate issues, borders on insanity, Laurie told me. “What we have to ask ourselves is what our children are going to think of us,” she said. “We’re being very self-destructive, but also deeply unethical. We’re not even trying to minimise how much worse it’s going to get. They’ll look back at all this science and how everything is changing, and see how we treated the damages so trivially and did so little.”

In 2010 some of the top departments in the US government got together to publish the first estimates of the money value of benefits from CO2 cuts. The benefits come from avoiding losses through damage caused by climate change. Called the social cost of carbon (SCC), this value is important because it affects rules on CO2 emissions, such as those from cars and power stations. Using three models that linked climate and economics, the government departments decided that the SCC was $21 per metric tonne of CO2*. Thanks to its importance for future climate rules, Laurie had watched the value being calculated closely – and was worried about what she saw.

“One of the models includes infectious disease damage estimates that are highly questionable,” she told me. “The models also estimate net gains from agriculture from now up to 2300 globally. By contrast the insurance industries appear to be estimating $25 billion dollars for crop losses in the US this year. That’s just one year for one country, and their calculation is for more than two hundred years, all countries. It also estimates a couple of billion in extreme weather damages globally over that period. Last year, in the US alone, there was over $50 billion dollars’ worth of extreme weather damage. Overall, it’s a very problematic estimate.” While the faults are plain, correcting any of these areas with more accurate values is a big problem itself. So Laurie and Chris looked at two other areas that they also felt had been worked out badly, but were simpler to tackle.

Could pollution be stopping warming’s impact on rain?

A brown cloud of pollution over Phoenix, Arizona. Brown clouds of aerosol pollutant particles could be overwhelming the expected changes in rainfall arising from increasing greenhouse gas levels in the air. Credit: Flick/Flickr

Contrary to previous predictions and measurements, rain patterns have got more uniform as the world has warmed over the past 70 years. So say Michael Roderick and his teammates from Australian National University, Canberra, who’ve developed an ‘accounting system’ that looks closely at where and when rain fell. And the reason could be aerosols – clouds of pollutant particles – produced by humans. “The existing dogma is that increasing greenhouse gas concentrations in the atmosphere have raised rainfall variability,” Michael told me. “In that context, our results emphasise the importance of taking a whole system approach in trying to understand how something complex, like rainfall, is changing in different places.”

When scientists want to understand how climate has been changing over large areas, they usually look at maps of long-term average data that ignore patterns of change in time, Michael explained. When they want to look at how it’s changed over time, they usually either look at a single place or a worldwide average, which ignores patterns in where the changes are. But Michael, along with fellow scientists Fubao Sun and Graham Farquhar, wanted to find a way to link place and time.

To do this Fubao started from a common statistical test called Analysis of Variance or ANOVA. Normally it’s used to compare the effect of different “treatments” – such as a variety of temperatures – on the yield of a crop, for example. In such cases each treatment must be repeated more than once, giving different “replicates”, for the test to be valid. ANOVA can be used to give a value for variance – a measure that shows how spread out an experiment’s measurements are.

Sun loses grip on Earth’s temperature changes

A solar flare in March that was the second largest since a period of low solar activity that started in 2007. For thousands of years solar activity has been linked to temperature patterns on Earth, but that link now seems to have been overwhelmed by other factors. Credit: NASA/SDO/AIA

Italian scientists say that the Sun has stopped directly causing temperature patterns on Earth. While the energy it blasts through space certainly still warms us, we no longer feel the effects of slight changes in its power. That’s what Antonello Pasini from the Institute of Atmospheric Pollution Research in Rome and his teammates say, after testing the various possible causes of the Earth’s temperature patterns.

“Our findings tell us that the causal link between solar radiation and global temperatures has weakened in recent decades,” Antonello told me. “This suggests that the Sun’s influence, which obviously exists and is strong, is probably overwhelmed by some other factors that at present are becoming more important in driving temperature changes. Further research is obviously needed on this topic, but my perception is that greenhouse gas emissions and other human influences are now strong enough to ‘obscure’ the Sun’s influence.”

The amount of energy the Sun produces varies, usually in regular 11-year cycles, and this has been an influence on the Earth’s temperature for thousands of years. But in research published in January, Antonello, along with Alessandro Attanasio and Umberto Triacca from the University of L’Aquila, found surprising evidence that this is no longer the case. They had tried out a test best known in economics, called Granger analysis and used to find out whether one set of events causes another, on climate science.

“We found that in recent decades there was a causal link – in the Granger sense – between greenhouse gases’ radiative forcing and the behaviour of global temperatures,” Antonello said. “The solar radiation did not show a significant link of this kind.” But Antonello, Alessandro and Umberto didn’t include weather patterns that bring natural variability to our climate, like El Niño and the Atlantic Multidecadal Oscillation (AMO), in that study. Now, by including them in a research paper published in the scientific journal Environmental Research Letters on Tuesday, they’ve been able to pin down when the Sun’s role faded away.

More bird flu over the horseshoe crabs’ nests?

Sandpipers, ruddy turnstones and red knot birds crowd Delaware Bay searching for horseshoe crab eggs. Credit: Paul Williams (Iron Ammonite)/Flickr

Climate change could make bird flu even more common among birds at a US hotspot for the disease. That’s what mathematical models of bird flu levels in Delaware Bay developed by biologists Pej Rohani and Vicki Brown at the University of Michigan in Ann Arbor suggest. “We’re not suggesting that our findings necessarily indicate an increased risk to human health,” said Pej. “But every single pandemic influenza virus that has been studied has included gene segments from avian influenza viruses. So from that perspective, understanding avian influenza transmission in its natural reservoir is, in itself, very important.”

Bird flu levels in Delaware Bay are at least ten times as high any other site in the world watched by scientists. That’s thanks in large part to ruddy turnstones, birds that pause there each year as they migrate between South America and the Arctic. Once in the Arctic, ruddy turnstones who spend their winters in America can meet – and share diseases – with others spending winter all over the world. During their Delaware stop-off they feed on horseshoe crab eggs, but fisherman harvest the crabs for fishing bait, while development in the area destroys the crabs’ nesting sites. This has meant fewer eggs, and in turn fewer shorebirds.

Global warming adds an extra layer to the problems facing these birds, by changing when important natural events happen. For example, birds that migrate long distances have started to make their spring journeys earlier. That could mean that ruddy turnstones arrive in Delaware Bay before all the horseshoe crabs have laid their eggs. Faced with an even more limited food supply, the birds must pack together yet closer in hunting for those that are available, creating an ideal scenario for disease transmission.