Archives for August 29, 2007

Article in The Australian:

Climate change can’t bog down APEC

NEXT week’s Asia-Pacific Economic Co-operation forum meeting in Sydney won’t be its last, but if we accept Kevin Rudd’s view of the world then, like John Howard, its days may be numbered.

The press release accompanying Rudd’s speech to the Australian Institute of International Affairs on Monday bore the headline, “APEC’S Future: Confront the Economic Challenge of Climate Change” . According to Labor’s Great Helmsman, if it fails to embrace “real action” on climate change, APEC has “little future”.

What does real action mean? To quote Rudd: “APEC must set concrete emissions targets, as it languishes behind the European Union and the G8 on tackling the economic impact of climate change.”

This is an interesting comparison, for reasons I will come to in a moment. But we already know that setting action plans in concrete is not APEC’s modus operandi.

China and the other Asian developing economies don’t want anything to do with Kyoto-style targets, which would cripple their economic growth. Bringing their living standards up to those of the West is their greatest economic challenge, not climate change.

A leaked draft of the Sydney Declaration to be released at the end of next week’s APEC meeting speaks only of a long-term aspirational target for emissions reductions. So presumably one of the early actions of a Rudd government will be to withdraw from APEC, an institution with little future………….

According to a report in The Australian, Labor plan to impose a ban on electric hot water systems from 2012, in favour of solar systems, in order to cut those ubiquitous greenhouse gas emissions. Read the full story here.

Thanks to Luke Walker for alerting us to this story. Luke asks if this is controversial fiddling or good science?

Graphic courtesy of NOAA

GREENHOUSE GASES LIKELY DROVE NEAR-RECORD U.S. WARMTH IN 2006

Greenhouse gases likely accounted for more than half of the widespread warmth across the continental United States last year, according to a new study by four scientists at NOAA’s Earth System Research Lab in Boulder, Colo. Last year’s average temperature was the second highest since record-keeping began in 1895. The team found that it was very unlikely that the 2006 El Niño played any role, though other natural factors likely contributed to the unusual warmth. The findings will appear September 5 in the Geophysical Research Letters, a publication of the American Geophysical Union.

The NOAA team also found that the probability of U.S. temperatures breaking a record in 2006 had increased 15-fold compared to pre-industrial times because of greenhouse gas increases in Earth’s atmosphere.

Preliminary data available last January led NOAA to place 2006 as the warmest year on record. In May, NOAA changed the 2006 ranking to second warmest after updated statistics showed the year was 0.08 degree F cooler than 1998.

The annual average temperature in 2006 was 2.1 degrees F above the 20th Century average and marked the ninth consecutive year of above-normal U.S. temperatures. Each of the contiguous 48 states reported above-normal annual temperatures and, for the majority of states, 2006 ranked among the 10 hottest years since 1895.

“We wanted to find out whether it was pure coincidence that the two warmest years on record both coincided with El Niño events,” says lead author Martin Hoerling of NOAA/ESRL. “We decided to quantify the impact of El Niño and compare it to the human influence on temperatures through greenhouse gases.” El Niño is a warming of the surface of the east tropical Pacific Ocean.

Using data from 10 past El Niño events observed since 1965, the authors examined the impact of El Niño on average annual U.S. surface temperatures. They found a slight cooling across the country. To overcome uncertainties inherent in the data analysis, the team also studied the El Niño influence using two atmospheric climate models. The scientists conducted two sets of 50-year simulations of U.S. climate, with and without the influence of El Niño sea-surface warming. They again found a slight cooling across the nation when El Niño was present.

To assess the role of greenhouse gases in the 2006 warmth, the NOAA team analyzed 42 simulations of Earth’s climate from 18 climate models provided for the latest assessment by the Intergovernmental Panel on Climate Change. The models included greenhouse gas emissions and airborne particles in Earth’s atmosphere since the late 19th century and computed their influence on average temperatures through 2006. The results of the analysis showed that greenhouse gases produced warmth over the entire United States in the model projections, much like the warming pattern that was observed last year across the country.

For a final check, the scientists compared the observed 2006 pattern of abnormal surface temperatures to the projected effects of greenhouse-gas warming and El Niño temperature responses. The U.S. temperature pattern of widespread warming was completely inconsistent with the pattern expected from El Niño, but it closely matched the expected effects of greenhouse warming.

When average annual temperature in the United States broke records in 1998, a powerful El Niño was affecting climate around the globe. Scientists widely attributed the unusual warmth in the United States to the influence of the ongoing El Niño.

“That attribution was not confirmed at the time,” says Hoerling. “Now we have the capability, on the spatial scale of the United States, to better distinguish natural climate variations from climate changes caused by humans.”

The authors also estimate that there is a 16 percent chance that 2007 will bring record-breaking warmth.

CNN’s take on the story is here:

Scorching U.S. heat in 2006 blamed on humans

Any reader not familiar with Milankovitch can read the Wiki write up here.

I’d already considered posting this interesting new Nature paper entitled ‘Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years,’ so when Luke Walker also drew my attention to it, I decided to give it a go.

The first paragraph summarises the paper:

The Milankovitch theory of climate change proposes that glacial–interglacial cycles are driven by changes in summer insolation at high northern latitudes. The timing of climate change in the Southern Hemisphere at glacial–interglacial transitions (which are known as terminations) relative to variations in summer insolation in the Northern Hemisphere is an important test of this hypothesis. So far, it has only been possible to apply this test to the most recent termination because the dating uncertainty associated with older terminations is too large to allow phase relationships to be determined. Here we present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations.

The paper states, “contrary to hypotheses ascribing the trigger of glacial terminations to CO2, obliquity (axial-tilt), or southern summer insolation, our chronology implicates northern summer insolation as the primary trigger.”

“In summary, the mean phasing of Antarctic climate, as well as the timing of the last four terminations and three post-interglacial coolings, are consistent with the hypothesis that high northern latitude summer insolation is the trigger of glacial–interglacial cycles. The role of CO2 as conveyor and amplifier of the orbital input should be quantified with climate models run using our new timescale; this quantification is important for future climate change predictions. Our timescale should be validated further with new radiometric age markers, as well as by process studies for complete understanding of the physical link between O2/N2 and local insolation. With future O2/N2 measurements, it may be possible to apply this method to the Dome Fuji and Dome C cores for termination V and older terminations, to investigate the phasing of climate and atmospheric composition with respect to orbital forcing further back in time.”

Fortunately, there is a write up here which makes it easier to understand compared with the original article:

“Strong Evidence Points to Earth’s Proximity to Sun as Ice age trigger”

A question unresolved for more than a century may have an answer Scripps Institution of Oceanography/UC San Diego

When do ice ages begin? In June, of course.

Analysis of Antarctic ice cores led by Kenji Kawamura, a visiting scientist at Scripps Institution of Oceanography, UC San Diego, shows that the last four great ice age cycles began when Earth’s distance from the sun during its annual orbit became great enough to prevent summertime melts of glacial ice. The absence of those melts allowed buildups of the ice over periods of time that would become characterized as glacial periods.

Results of the study appear in the Aug. 23 edition of the journal Nature.

Jeff Severinghaus, a Scripps geoscientist and co-author of the paper, said the finding validates a theory formalized in the 1940s but first postulated in the 19th Century. The work also helps clarify the role of carbon dioxide in global warming and cooling episodes past and present, he said.

“This is a significant finding because people have been asking for 100 years the question of why are there ice ages,” Severinghaus said.

A premise advanced in the 1940s known as the Milankovitch theory, named after the Serbian geophysicist Milutin Milankovitch, proposed that ice ages start and end in connection with changes in summer insolation, or exposure to sunlight, in the high latitudes of the Northern Hemisphere. To test it, Kawamura used ice core samples taken thousands of miles to the south in Antarctica at a station known as Dome Fuji.

Scientists studying paleoclimate often use gases trapped in ice cores to reconstruct climatic conditions from hundreds of thousands of years in the past, digging thousands of meters deep into ice sheets. By measuring the ratio of oxygen and nitrogen in the cores, Kawamura’s team was able to show that the ice cores record how much sunlight fell on Antarctica in summers going back 360,000 years. The team’s method enabled the researchers to use precise astronomical calculations to compare the timing of climate change with sunshine intensity at any spot on the planet.

Kawamura, a former postdoctoral researcher at Scripps, used the oxygen-nitrogen ratio data to create a climate timeline that was used to validate the calculations Milankovitch had created decades earlier. The team found a correlation between ice age onsets and terminations, and variations in the season of Earth’s closest approach to the sun. Earth’s closest pass, or perihelion, happens to fall in June about every 23,000 years. When the shape of Earth’s orbit did not allow it to approach as closely to the sun in that month, the relatively cold summer on Earth encouraged the spread of ice sheets on the Northern Hemisphere’s land surface. Periods in which Earth passed relatively close in Northern Hemisphere summer accelerated melt and brought an end to ice ages…………

…..The team found that the changes in Earth’s orbit that terminate ice ages amplify their own effect on climate through a series of steps that leads to more carbon dioxide being released from the oceans into the air. This secondary effect, or feedback, has accounted for as much as 30 percent of the warming seen as ice ages of the past have come to an end…..