Archive for the ‘Climate extremes’ Category
An excellent briefing from Paul Rogers of the Oxford Research Group on food security and climate change is updating the current global situation with respect to recent climate events (Hat tip to Jamie Doughney). I’ll reproduce it below after making a few comments.
Most of the briefing concentrates on the conditions of the 1974 food crisis to add a historical perspective. Globally, the US and North America is in the second year of drought, looking at greatly reduced maize production and other other crops. The southwest Indian monsoon is somewhat late and currently at 17% below the 50-year average after a poor year last year. The Horn of Africa is in a delicate recovery stage after last year’s disaster, and efforts to build resilience in the region are ongoing. A recent report from scientists at the UK’s Met Office and the USA’s National Oceanographic and Atmospheric Administration (NOAA) found that the number of below average rainy seasons in East Africa could have been attributable to warming in the Indian and Western Pacific Oceans.
Rogers states that economic growth has been patchy, so that the proportion of people under food stress has not changed greatly since the 1970s. This time around though, he nominates climate change as making a significant contribution to that stress. I agree. One part of that is the asymmetric impact of warming on land affecting drier regions. This is pretty well known. The other is that he suggests climate change is accelerating:
The loss of Arctic sea in recent summers has exceeded forecasts using climate modelling and some recent events have been startling in their intensity, including the extent of the thawing of surface layers of the Greenland ice cap during the early part of July.
This is because climate change is strongly non-linear, and there is increasing evidence that the world, or at least much of the northern hemisphere, is in a warming episode similar to that experienced in 1997-98. The idea that extremes should change gradually on a smoothly changing mean climate is seriously wrong, and if the world continues to adapt based on that assumption, millions of people will continue to be at risk through insufficient adaptation efforts.
I’m champing at the bit to get back to this research because I use different methods to those of mainstream climate science (but also have a truckload of other work to do). However, both lines of research are pointing to a strong climate change signal in recent extreme events, thereby increasing scientific confidence in its conclusions.
Rogers’ briefing is reproduced below.
A couple of my recent forays into the media have provoked comment below the articles themselves and in emails sent querying particular points. They are worth unpacking because they reflect on the different between the straight communication of science and framing risk.
One was in reference to a recent op-ed in The Age. In it, I said:
If people accept the 0.0038 and 0.02 degree benefits as valid then they also accept the science behind a 5.3 degrees warming for business as usual (As in the emission scenario created by Treasury for the 2008 Garnaut Review). Who wants to live in a world warming by 5 degrees or more? Major food crops could not be grown in many parts of the world, projected sea level rise would be tens of metres, most of the shelled species in the ocean would not survive, ecosystems would be disrupted as the pace of change outstripped their ability to adapt and millions to billions of people would lose environmental security leading to mass migrations never before seen.
That prompted an email from an earth scientist wanting to know what peer-reviewed reference I was using for the projected tens of metres of sea level rise. I sent back this now famous diagram and a note saying that I wasn’t putting it on a timetable. He then replied suggesting that people could be misled into thinking that the date was 2100 (because that was tied to the two temperature measures) and that I was being alarmist. Because it would take thousands of years to be realised. Read the rest of this entry »
Been meaning to post on Paul Durack, Susan Wijfells and Richard Matear’s work on the intensification of the global water cycle using changing ocean salinity, but Paul has written a great article for The Conversation (reproduced below). Paul and I used to give each other grief when we were both at CSIRO, so for light relief he went and did a Ph D, doing this great work in the process.
The work cracked Science magazine (full article behind paywall) and has been featured on Real Climate. It has also attracted a rejoinder in correspondence by Roderick and colleagues who maintain that the evidence of an intensified rainfall response on land is not there (all of which is behind a paywall). I reckon they’re wrong and there is growing evidence that the models are understating hydrological sensitivity. This means that droughts and floods are changing faster than projected by the models. Furthermore, I think these changes are strongly non linear as has been observed in south-eastern Australia – something that Paul is a bit dubious about (for the moment!). Anyhow, from the man himself, read on … Read the rest of this entry »
The full IPCC Special Report Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) has been released. The download of the entire report (44 Mb) is here, the Summary for Policymakers is here, the press release is here and slide presentation (pdf) here. Also on the site are individual chapters for download, review comments, process information, graphics and the grey literature library.
As I posted late last year with the release of the SPM, the great benefit of this special report is the coming together of the climate change and disaster management expert communities. A marriage, which I’m told, got a bit rocky at times. The report emphasises the need to address both biophysical and social-economic aspects of changing climate extremes and the systems exposed to those changes. Read the rest of this entry »
SOUTHEASTERN Australia could be shocked by a surge in wild bushfires and heatwaves, according to research suggesting that scientists might have underestimated the suddenness of future climate change impacts.
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.
The Sacred Cowboys sang nothing grows in Texas. Last summer it came true. The Texan drought of 2011 was hotter and drier than any of the great droughts of the 1930s. Is it possible to diagnose what role climate change may have played? State Climatologist for Texas John Nielsen-Gammon asked this question last year in a preliminary post on the drought.
He concluded there was a strong anthropogenic evidence for warming but little evidence for its influence on the extremely low rainfall. The following analysis was developed without seeing his summary and happily, they have much in common. The big difference is the explicit treatment of non-linear warming.
I applied the methods for analysing step changes and attributing regional warming developed for SE Australia to the Texan climate. Was it possible to estimate the relative contributions of global warming for a single season? The results were more successful than I had anticipated. Tmax was 86% more likely to be due to anthropogenic warming and Tmin 95%. The method is unorthodox, so may be controversial. Details over the fold. Read the rest of this entry »