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Saturday, November 26, 2011

Pacific climate change: temperatures rise, sea levels increase, rainfall changing

A major new report on climate change in the Pacific Ocean region reports that the region is getter hotter, sea levels are rising, rainfall is changing and equatorial winds have weakened. While cyclone may tend to decrease slightly in the future, cyclone intensity is likely to be greater.

The report launched today - Climate change in the Pacific, scientific assessment and new research - contains 530 pages in 2 volumes with over 100 authors. The research was led by the Australian Bureau of Meteorology (BOM) and Commonwealth Scientific Industrial Research Organisation (CSIRO) with strong input from 15 National Meteorological Services, Geoscience Australia, and from universities in the region. The report includes observations and climate projections for 15 partner countries involved : Cook Islands, East Timor, Federated States of Micronesia, Fiji, Kiribati, Marshall Islands, Nauru, Niue, Palau, Papua New Guinea, Samoa, Solomon Islands, Tonga, Tuvalu, and Vanuatu.

Dr Scott Power, Senior research scientist from Australian Bureau of Meteorology (BOM), outlined the primary findings in a media conference on Frday November 25 hosted by the Australian Science Media centre. He reported:

  • The Pacific region is getting hotter
  • Sea levels are rising
  • Rainfall is changing
  • Equatorial winds have weakened
  • Further warming and sea level rise in response to human forced greenhouse gas emissions seem inevitable

According to Dr Power, long term trends we have seen are accompanied by a great deal of naturally occurring variability linked to major cyclical weather patterns like the El Nino Southern Oscillation (ENSO) cycle. But the natural variability alone can't explain past climate and will not wholly determine future climate trends.

An important conclusion of the report is that the magnitude of human forced changes can be reduced if global greenhouse gas emissions are reduced.

According to the observed changes CO2 concentrations are now higher than they have been for hundreds of thousands of years.

  • Humans are primarily responsible for this increase.
  • Research over the past century clearly shows that higher greenhouse gas concentrations warm the planet.
  • All Pacific island stations have warmed over the past 50 years, most in the range 0.4 degrees to -1.0 degrees C. The regional warming observed over the Pacific matches the warming trend observed on a global basis.
  • Global sea-level has risen by 1.7mm/yr since 1900 and twice this rate since 1993. Rise in the Pacific since 1993 is much larger than this in the west, much less in the east.
  • The top 200m of the ocean has warmed
  • The Pacific Ocean has become more acidic
  • No significant trends in tropical cyclones (though records for Pacific are short)

Kevin Hennessy, Principal research scientist from the CSIRO, explained that researchers looked at 24 global climate models and found 18 useful for looking at regional scenarios in three 20 year periods with three emission scenarios. The projections found that:

  • 2030: 0.5 to 1.0oC warmer, regardless of the emissions scenario
  • 2055: 1.0 to 1.5oC warmer with regional differences depending on the emissions scenario
  • 2090: the warming is around 1.5 to 2.0oC for B1 (low emissions); 2.0 to 2.5oC for A1B (medium emissions); 2.5 to 3.0oC for A2 (high emissions)
  • Large increases in the frequency of extremely hot days and warm nights
  • Increases in annual mean rainfall over most of the region, especially along the equator, but small decreases during "dry season" (May-Oct) in some countries
  • Tropical cyclone numbers are likely to decline in the Pacific Ocean over the 21st century
  • Many simulations with fine resolution models (downscaling) show an increase in the proportion of the most severe cyclones

Kevin Hennessy explained on ABC radio: "It is very difficult to almost have a competition as to who is the most vulnerable. Each are vulnerable in different ways and it is very difficult to get a standard measure or metric that can compare them on equal terms. I think it is sufficient to say that all the western tropical Pacific countries are exposed to projected changes and extreme temperatures and extreme rainfall, ocean acidification and sea level rise. Some of the low lying coral atolls are especially exposed to sea level rise and storm tides and most of the countries that we've look at are exposed to changes in tropical cyclones except those that are right along the equator. And many of the mountainous countries in the region are particularly exposed to land slides."

For Sea-level rise in the region is likely to be similar to the global average. o By 2090 sea level rise is likely to be 17-46 cm (B1 scenario), 20-58 cm (for A1B scenario), and 21-60 cm (for A2 scenario). The study noted that Improved understanding of ice sheet dynamics is needed to improve projections of sea level rise. (see Also Sea Level rise and Australia)

The recent IPPC paper on Extreme weather and Climate change - Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) - particularly mentioned sea level rise as an important risk factor for small island nations:

"It is very likely that mean sea level rise will contribute to upward trends in extreme coastal high water levels in the future. There is high confidence that locations currently experiencing adverse impacts such as coastal erosion and inundation will continue to do so in the future due to increasing sea levels, all other contributing factors being equal. The very likely contribution of mean sea level rise to increased extreme coastal high water levels, coupled with the likely increase in tropical cyclone maximum wind speed, is a specific issue for tropical small island states."

Many of the Island nations are dependent on the health of reef ecosystems for food and tourism. Reef ecosystems are likely to be compounded by other stressors including coral bleaching, storm damage and fishing pressure.

The oceans provide a giant carbon sink absorbing huge quantities of CO2. However absorption of CO2 causes ocean acidification and a decrease in aragonite saturation. Aragonite values less than 3.5 result in stress for coral - they cannot keep building their coral structures. Values of less than 3.5 will be reached by 2050 in much of the Pacific, and will continue to decline.

The Pacific Climate Change Science Program has set up an interactive website showing data and projections for each Pacific Island nation or region.

The full report will be presented at the United Nations Framework Convention on Climate Change (UNFCCC) negotiations to take place for 2 weeks in Durban South Africa from late November 2011. Individual report chapters and country summaries can be downloaded as PDF files.

Two years ago at the Copenhagen climate talks Tuvalu made a heart wrenching stand and plea for action on reducing greenhouse gas emissions and setting a 1.5 degree limit on the temperature increase to prevent the innundation and ultimate disappearance of small island nations like Tuvalu from rising sea levels caused by global warming.

I first started talking and blogging about the impact on climate change and rising seas on small island states in 2005 - Climate Change and Development Issues for Island States.

Will anything change at Durban?

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