Archive for the ‘Sea level rise’ Category
Warmer oceans, tropical species being found further south, decline in temperate species, the first signs of CO2 effects on shell production in Australian waters …
These are a few of the headlines from the Marine Climate Change in Australia, Impacts and Adaptation Responses 2012 Report Card (download pdf). Put together by the Marine Biodiversity and Resources Adaptation Network (NCCARF), Fisheries Research and Development Corporation, and CSIRO’s Climate Adaptation Flagship. The reporting comprehensive, covering the report card itself and six chapters on marine climate and thirteen on marine biodiversity. Alistair Hobday, summarising the report card on The Conversation.
Here’s a summary with some of my own conclusions about observed and projected changes. The latter you can take or leave as they’re based on my personal views about how climate changes. For recent and near future changes, I place a greater emphasis on how climate is likely to change rather than by how much. This places the emphasis more on the diagnosis and understanding of change rather than prediction. There’s a fair bit in doing this, so amongst other things I’m into today (like gardening, cooking and cleaning), I’ll update these sections as I go (Sunday 11 am, SST; Wednesday, SLR). Read the rest of this entry »
Yesterday the Bureau of Meteorology and CSIRO released their State of the Climate 2012 report and today the Climate Commission released The science behind southeast Australia’s wet, cool summer. Both documents outline the latest changes with clear explanations and useful diagrams.
State of the Climate 2012 showed a general trend toward increased spring and summer monsoonal rainfall across Australia’s north, and a decline in late autumn and winter rainfall across southern Australia.
Sea-levels had risen around Australia at rates equal to or greater than the global average, and sea-surface temperatures in the region had increased faster than the global average.
State of the Climate 2012 documents the annual growth in global fossil-fuel CO2 emissions and other greenhouse gases. The CO2 concentration of the atmosphere had risen to around 390 parts per million in 2011, a level unprecedented in the past 800,000 years. During the past decade it has risen at more than 3% per year, which is projected to cause significant further global warming.
The Climate Commission Report was written by Professors Will Steffen, Matt England and David Karoly:
Most parts of Australia have experienced exceptionally heavy rains over the past two years, filling many dams around the country and breaking the drought of 1997–2009. There has been much confusion in the media about what this means for climate change. This report seeks to set the record straight.
The main point for me, which I fully endorse:
Climate change cannot be ruled out as a factor in recent heavy rainfall events. The Sea Surface Temperatures (SSTs) around northern Australia during the spring and early summer of 2010–2011 were the highest on record. This has very likely contributed to the exceptionally heavy rainfall over much of Australia in the last two years. La Niña events bring high SSTs to the seas around northern Australia, but warming over the past century has also contributed to the recent record high SSTs.
Sea level rise Part I covered the stoush resulting from a paper on long-term tide gauge records for Australasia. The author was Phil Watson of the NSW Department of Environment, Climate Change and Water and the paper was published in the Journal of Coastal Research in March. Tamino has pointed out the limitations of the statistical methods used, showing that the conclusion of decelerating sea level cannot be sustained. Tamino removed the annual cycle then used 20-year and lowess smoothing to show that the opposite conclusion – recent sea level rise is accelerating – is probably true for the Australasian region. A conclusion I strongly support.
It’s generally accepted that long-term climate records are analysed using trend analysis; either as a linear or non-linear trend, usually quadratic. The use of a particular statistical method assumes a specific model of how a system behaves. That model can be made explicit but if not, there is still an assumed model being used. Sometimes the assumption won’t be declared because it’s a widely accepted paradigm.
So what is the model sitting behind trend analysis – measured as either a straight line or a curve – and what paradigm of change process does it support? By analysing single tide gauge records, I am asking “How does sea level respond to externally-driven warming at a given location?” Read the rest of this entry »
A stoush on Australiasian sea level rise has erupted in the press and the blogosphere since the publication on July 22 of a story in The Australian covering a paper analysing long tide gauge records in Australasia. The details are covered comprehensively by Deltoid. The paper, by Phil Watson of the NSW Department of Environment, Climate Change and Water was published in the Journal of Coastal Research in March. It concluded that:
The analysis reveals a consistent trend of weak deceleration at each of these gauge sites throughout Australasia over the period from 1940 to 2000. Short period trends of acceleration in mean sea level after 1990 are evident at each site, although these are not abnormal or higher than other short-term rates measured throughout the historical record.
The Australian misprepresented this conclusion by calling in question 21st century projections of sea level rise (SLR). There is a very simple reason as to why this is not the case. The projections are about current and future ocean budgets, whereas the tide gauge records are more about process. Sea level budgets are known well enough to provide very high confidence that SLR will accelerate throughout the 21st century. The process of sea level rise at a site as measured by tide gauges is complex. Watson’s conclusions as emphasised by himself, his employers and real experts do not call into question the basic science about future SLR budgets.
However, as to the process of SLR I think the statistics currently being used don’t tell the full story. In part I, I summarise the story to date and in Part II, I will show an alternative method for analysing long-term tide gauge records. Read the rest of this entry »