28 June 2017, The Conversation, The world’s tropical zone is expanding, and Australia should be worried. The Tropics are defined as the area of Earth where the Sun is directly overhead at least once a year — the zone between the Tropics of Cancer and Capricorn. However, tropical climates occur within a larger area about 30 degrees either side of the Equator. Earth’s dry subtropical zones lie adjacent to this broad region. It is here that we find the great warm deserts of the world.Earth’s bulging waistline Earth’s tropical atmosphere is growing in all directions, leading one commentator to cleverly call this Earth’s “bulging waistline”. Since 1979, the planet’s waistline been expanding poleward by 56km to 111km per decade in both hemispheres. Future climate projections suggest this expansion is likely to continue, driven largely by human activities – most notably emissions of greenhouse gases and black carbon, as well as warming in the lower atmosphere and the oceans. If the current rate continues, by 2100 the edge of the new dry subtropical zone would extend from roughly Sydney to Perth. As these dry subtropical zones shift, droughts will worsen and overall less rain will fall in most warm temperate regions. Poleward shifts in the average tracks of tropical and extratropical cyclones are already happening. This is likely to continue as the tropics expand further. As extratropical cyclones move, they shift rain away from temperate regions that historically rely upon winter rainfalls for their agriculture and water security. Researchers have observed that, as climate zones change, animals and plants migrate to keep up. But as biodiversity and ecosystem services are threatened, species that can’t adjust to rapidly changing conditions face extinction. In some biodiversity hotspots – such as the far southwest of Australia – there are no suitable land areas (only oceans) for ecosystems and species to move into to keep pace with warming and drying trends. We are already witnessing an expansion of pests and diseases into regions that were previously climatically unsuitable. This suggests that they will attempt to follow any future poleward shifts in climate zones. Read More here
Category Archives: Impacts Observed & Projected
26 June 2017, Washington Post, Sea level rise isn’t just happening, it’s getting faster. In at least the third such study published in the past year, scientists have confirmed seas are rising, and the rate of sea level rise is increasing as time passes — a sobering punchline for coastal communities that are only now beginning to prepare for a troubling future. What was a 2.2 millimeter per year rise in 1993 was a 3.3 millimeter rise in 2014, based on estimates of the mass changes of a number of key components of sea level rise, such as the melting of the Greenland and Antarctic ice sheets, the study in Nature Climate Change found. That’s the difference between 0.86 and 1.29 inches per decade — and the researchers suggest further sea level acceleration could be in store. The chief cause of the acceleration was the melting of the Greenland ice sheet, which went from contributing under 5 percent of all sea level rise in 1993 to contributing over 25 percent in 2014, the study found. The loss of ice in Antarctica and smaller glaciers over the same time period also contributed to quicker sea level rise. The increase in the rate of sea level rise “highlights the importance and urgency of mitigating climate change and formulating coastal adaptation plans to mitigate the impacts of ongoing sea level rise,” write Xianyao Chen of the Ocean University of China and Qingdao National Laboratory of Marine Science and Technology, and colleagues. Chen’s co-authors hailed from institutions in China, Australia and the United States. “We understand why the sea level is accelerating and we’re understanding what the components are contributing,” said Christopher Harig, one of the study’s authors and a researcher at the University of Arizona. Earlier this year, a different group of researchers found sea level rise was only about 1.1 millimeters per year before 1990, whereas in the period between 1993 through 2012 it was 3.1 millimeters per year. NASA, at present, puts the rate of sea level rise at 3.4 millimeters per year. But while the individual estimates differ, the broader picture is that researchers generally agree that the rate of sea level rise is increasing — and that this will have major consequences for coastal regions, which will have less time to adapt if sea level rise acceleration continues. Read More here
19 June 2017, The Conversation, Are heatwaves ‘worsening’ and have ‘hot days’ doubled in Australia in the last 50 years? The release of the Finkel report has refocused national attention on climate change, and how we know it’s happening. On a Q&A episode following the report’s release, Climate Council CEO Amanda McKenzie said we’ve seen: … worsening heatwaves, hot days doubling in Australia in the last 50 years. ….There’s not a large body of research against which to test this claim. But the research we do have suggests there has been an observable increase in the frequency and intensity of heatwaves in Australia. Research published in 2013 found a trend towards more heat waves in Australia between 1951 and 2008. A review paper published in 2016 assessed evidence from multiple studies and found that heatwaves are becoming more intense and more frequent for the majority of Australia. The following chart shows heatwave days per decade from 1950 to 2013, highlighting a trend toward more heatwave days in Australia over time: Read More here
1 June 2017, The Conversation, Global stocktake shows the 43 greenhouse gases driving global warming. The most comprehensive collection of atmospheric greenhouse gas measurements, published today, confirms the relentless rise in some of the most important greenhouse gases. The data show that today’s aggregate warming effect of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) is higher than at any time over the past 800,000 years, according to ice core records. Building on half a century of atmospheric measurements by the international research community, we compiled and analysed the data as part of a group of international scientists, led by Malte Meinshausen from the University of Melbourne in collaboration with CSIRO. Together, the data provide the most compelling evidence of the unprecedented perturbation of Earth’s atmosphere. They clearly show that the growth of greenhouse gases began with the onset of the industrial era around 1750, took a sharp turn upwards in the 1950s, and still continues today. Research has demonstrated that this observed growth in greenhouse gases is caused by human activities, leading to warming of the climate – and in fact more than the observed warming, because part of the effect is currently masked by atmospheric pollution (aerosols). The new collection of records comes from measurements of current and archived air samples, air trapped in bubbles in ice cores, and firn (compacted snow). The data cover the past 2,000 years without gaps, and are the result of a compilation of measurements analysed by dozens of laboratories around the world, including CSIRO, the Bureau of Meteorology’s Cape Grim Station, NOAA, AGAGE and the Scripps Institution of Oceanography, among others. Read More here