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| Changes in average temperature for Australia for each year (orange line) and each decade (grey boxes), and 11-year average (black line – an 11-year period is the standard used by the Intergovernmental Panel on Climate Change). Anomalies are the departure from the 1961-1990 average climatological period. The average value for the most recent 10-year period (2002–2011) is shown in darker grey. Bureau of Meteorology |
That's right, CO levels have not been as high today in the last 15 million years!!
The report is right in saying that DIRECT evidence (from analysing atmospheric bubbles trapped in Antarctic ice cores, drilled down to ice 800,000 year old) only goes back that far. But new research from the paleoclimate record using proxy data allow estimation back much further.
The evidence is presented in a research paper in 'Science' in October 2009 by Aradhna Tripati at UCLA and colleagues, entitled Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years. Tripati's conclusion is stark:
The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit [DS: 3 to 6 degrees Celsius] higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland,Here is how UCLA describes the findings:
By analyzing the chemistry of bubbles of ancient air trapped in Antarctic ice, scientists have been able to determine the composition of Earth's atmosphere going back as far as 800,000 years, and they have developed a good understanding of how carbon dioxide levels have varied in the atmosphere since that time. But there has been little agreement before this study on how to reconstruct carbon dioxide levels prior to 800,000 years ago.Tripati describes her work:
Tripati, before joining UCLA's faculty, was part of a research team at England's University of Cambridge that developed a new technique to assess carbon dioxide levels in the much more distant past — by studying the ratio of the chemical element boron to calcium in the shells of ancient single-celled marine algae. Tripati has now used this method to determine the amount of carbon dioxide in Earth's atmosphere as far back as 20 million years ago.
We are able, for the first time, to accurately reproduce the ice-core record for the last 800,000 years — the record of atmospheric C02 based on measurements of carbon dioxide in gas bubbles in ice....This suggests that the technique we are using is valid.Tripati says it was "A slightly shocking finding", because
We then applied this technique to study the history of carbon dioxide from 800,000 years ago to 20 million years ago. We report evidence for a very close coupling between carbon dioxide levels and climate. When there is evidence for the growth of a large ice sheet on Antarctica or on Greenland or the growth of sea ice in the Arctic Ocean, we see evidence for a dramatic change in carbon dioxide levels over the last 20 million years.
is that the only time in the last 20 million years that we find evidence for carbon dioxide levels similar to the modern level of 387 parts per million was 15 to 20 million years ago, when the planet was dramatically different.It has been know from ice cores that CO2 levels have varied only between 180 and 300 parts per million over the last 800,000 years, and that todays CO2 levels are unprecedented over that period. But the findings from Tripati et al. that modern levels have not been reached in the last 15 million years is new. [In the last 20 million years, key features of the climate record include the sudden appearance of ice on Antarctica about 14 million years ago and a rise in sea level of approximately 75 to 120 feet.]
Tripati's says her new chemical technique has an average uncertainty rate of only 14 parts per million, and "We can now have confidence in making statements about how carbon dioxide has varied throughout history." She says:
We have shown that this dramatic rise in sea level is associated with an increase in carbon dioxide levels of about 100 parts per million, a huge change," Tripati said. "This record is the first evidence that carbon dioxide may be linked with environmental changes, such as changes in the terrestrial ecosystem, distribution of ice, sea level and monsoon intensity.Don't say you weren't warned!
David Spratt
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Here is the statement accompanying the CSIRO/BoM report's release:
State of the Climate 2012
Wednesday, 14 March 2012
Australia’s land and oceans have continued to warm in response to rising CO2 emissions from the burning of fossil fuels.
This is the headline finding in the State of the Climate 2012, an updated summary of Australia’s long term climate trends released by CSIRO and the Bureau of Meteorology today (14 March 2012).
CSIRO Chief Executive, Dr Megan Clark, said the latest analysis painted a clear decade-to-decade picture of Australia’s climate, while at the same time noting its highly variable nature from one year to the next.
“Much of Australia may have lurched from drought to floods since the previous State of the Climate, but this has occurred against a backdrop of steadily increasing air and ocean temperatures and rising sea levels. What’s more, the rate of change is increasing.
“The fundamental physical and chemical processes leading to climate change are well understood, and CSIRO and the Bureau of Meteorology observations demonstrate that change is occurring now,” said Dr Clark.
Bureau of Meteorology Acting Director, Dr Rob Vertessy, said this updated summary was based on improved understanding drawn from detailed analysis of our national climate record, which goes back more than a hundred years.
“Ground, ocean and satellite based observations are giving us highly consistent observations of this warming trend. State of the Climate 2012 confirms that each decade has been warmer than the previous decade since the 1950s, with an increase in the number of warm nights, and more monthly maximum temperature records being broken.
“CSIRO and the Bureau of Meteorology will continue to provide observations, projections, research, and analysis so that Australia’s responses to the challenges of a changing climate are underpinned by robust scientific evidence of the highest quality,” said Dr Vertessy.
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 CO2concentration 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.
Key points
Temperature
- Each decade has been warmer than the previous decade since the 1950s.
- Australian annual-average daily maximum temperatures have increased by 0.75 °C since 1910.
- Australian annual-average daily mean temperatures have increased by 0.9 °C since 1910.
- Australian annual-average overnight minimum temperatures have warmed by more than 1.1 °C since 1910.
- 2010 and 2011 were Australia’s coolest years recorded since 2001 due to two consecutive La Niña events
- Southwest Western Australia has experienced long-term reductions in rainfall during the winter half of the year.
- There has been a trend over recent decades towards increased spring and summer monsoonal rainfall across Australia’s north, higher than normal rainfall across the centre, and decreased late autumn and winter rainfall across the south.
- Global-average mean sea level for 2011 was 210 mm above the level in 1880.
- Global-average mean sea level rose faster between 1993 and 2011 than during the 20th century as a whole.
- The heat content of the world’s oceans has increased during recent decades, increasing the volume of ocean waters and contributing to sea-level rise.
- Sea-surface temperatures around Australia have increased faster than the global average.
- Sea-surface temperatures in the Australian region in 2010 were the highest on record.
- Sea-surface temperatures have increased by about 0.8 °C since 1910.
- Fossil-fuel CO2 emissions increased by more than 3 per cent per year from 2000 to 2010.
- The concentration of CO2 in the atmosphere in 2011 was 390 parts per million – higher than at any time for the past 800,000 years.
- The main cause of the observed increase in CO2 concentration in the atmosphere is the combustion of fossil fuels since the industrial revolution.
- Both natural and human influences affected climate over the past 100 years.
- It is very likely that most of the surface global warming observed since the mid 20th century is due to anthropogenic increases in greenhouse gases.
- Human activities also have influenced ocean warming, sea-level rise, and temperature extremes.
- The warming around Australia is consistent with the global pattern and cannot be explained by natural variability alone.
- There is evidence of changes in extreme temperatures globally.
- No significant trends in the total numbers of tropical cyclones or in the occurrence of the most intense tropical cyclones have been found in the Australian region
- Australian average temperatures are projected to rise by 1.0 to 5.0 °C by 2070 when compared with the climate of recent decades.
- An increase in the number of droughts is expected in southern Australia but it also is likely that there will be an increase in intense rainfall events in many areas.
