30 June 2007


Some relevant (and interesting) links via Climate Progress:

UN: Floods, heatwaves send signal about global warming - Mail and Guardian Online

"Heavy rainfalls in Pakistan, India and northern England and heatwaves in Greece, Italy and Romania are indications of what might happen more frequently and more severely across the globe as a consequence of global warming," said Salvano Briceno, director of the UN International Strategy for Disaster Reduction.

"We cannot wait to be taken by surprise; we know what is going to happen and we can prepare for it," he added.
No direct attribution of these events to climate change, but stating that this is consistent with what is expected to happen...How long do these things have to happen before we decide it is due to climate change?

Climate changes are making poison ivy more potent - Wall Street Journal Online

The latest research, led by Dr. Ziska, studied poison ivy plants in Maryland under different levels of carbon-dioxide exposure. One group of plants was exposed to about 300 parts per million of carbon dioxide -- about the same level found in the atmosphere in the 1950s. Another group was exposed to 400 parts per million of CO2 -- about the same level in the atmosphere today.

After about eight months, leaf size, stem length and weight and oil content of the plants raised at current carbon-dioxide levels were, on average, 50% to 75% higher than the plants under the 1950s conditions, according to the study, expected to be published this year in the journal Weed Science. Not only did the higher CO2 level double the growth rate, but it made for hardier plants that recovered more quickly from the ravages of grazing animals.

Oh joy! What a swell way to alter the ecosystem!

27 June 2007

Arabian Sea cyclones

June has seen the formation of two tropical cyclones in the Arabian Sea. The first, the formation of Cyclone Gonu in early-June was a highly unusual storm being the first Category 5 TC to be observed over the northern Arabian Sea. As seen in the satellite image at left, the cyclone had a quite distinct eye and was quite powerful.

The second storm, named Cyclone 03B, initially formed in the Bay of Bengal, dissipated and reformed over the Arabian Sea. Its strength was more typical of Arabian Sea TC, reaching only tropical storm strength.

At this time of the season, two events this close together, along with the intensity of Gonu is quite rare
. Arabian Sea SSTs have recently been 1-2 C warmer than normal, particularly in early-June, which likely contributed to the strength of Gonu. These anomalies have been decreasing in strength since that time.

Tropical cyclone climatology suggests a small peak in TCs in May/June and a stronger peak in October/November for the entire north Indian Ocean basin...(see Fig 1.23). More of the storms reaching cyclone strength (65 kts; Fig 1.10) occur in the Bay of Bengal. Over the Arabian Sea, typically there are 5-20 cyclones per 100 years from any given point within the sea. The main focus of that activity lies in the eastern portion of the Sea. This figure, showing TC tracks over the N. Indian basin for the previous 25 years or so, summarizes these aspects of the climatology nicely.

Is this event an impact of climate change? The answer must be a qualified maybe. There is no doubt that Gonu, in particular, was an unusual event. We cannot be absolutely sure as to how unprecedented this event truly is. The data just aren't there. That said, it is just one more event in the (apparent) global trend of more frequent extreme events consistent with the hypothesis of anthropogenic climate change.

21 June 2007

A return to the good ol' days?

Much of Australia is experiencing a what has been termed a 1-in-a-100 year (or 1000 year, in some cases) drought. Recent rains notwithstanding, the drought continues over most of the country.

Dr Hamish McGowan of University of Queensland has created a reconstruction of the climate for the past 40 000 years from peat samples taken in SE QLD. From these records, the past 5000 years have apparently been drier than the current worst drought on record...

The proxy record also indicates that the Southern Hemisphere is not isolated from past large-scale climate changes in the rest of the world

OK, so the climate of Australia has been worse in the past. It still begs the question of why these changes are happening now.

Europe's warm winter

It appears that the past winter in Europe has been the warmest in 700 years. Taken singly, autumn 2006 and winter 2007 were only the warmest in 500 years, but the combination of the two produced the 700 years number.

There were also unusual phenological events with, for example hazel trees in Germany blossoming a month earlier than anytime in the past 50 years.

Still, this single event cannot be attributed explicitly to climate change...

Geophysical Research Letters (DOI: 10.1029/2007GL029951)