By Mike Ritchie, MRA Consulting Group
The east coast of Australia suffered through a severe heatwave a few weeks ago. To borrow the phrase, a single heatwave is no more evidence of climate change, than a single swallow is of summer.
The evidence for climate change doesn’t neatly announce itself through a particular weather event. Instead, it makes itself known through persistent increases in warming data, the frequency and severity of multiple weather events and observable changes in long term trends. Here is some of the science and the organisations producing it:
- The Bureau of Meteorology reports that Australia’s ten hottest years on record have been in the years since 1980. And of those ten hottest years, six have been between 2005 and 2016.
- It’s not just Australia that is getting hotter. The World Meteorological Organization (WMO) reports that global mean temperature for 2016 was the hottest on record. The hottest year before that? 2015. WMO reports that the global average is now 1.1 degrees Celsius above the pre-industrial era.
- The NOAA, reports that more than 90 percent of the Earth’s warming over the past 50 years has occurred in the ocean, and that heat increase has been measured down to 700 metres below sea level.
- Unsurprisingly, the Bureau of Meteorology reports that for sea surface temperatures in the Australian region, the last seven years have been in the ten warmest years on record.
- With oceans getting hotter, we’d expect to observe higher sea levels since water expands as it warms. The CSIRO reports that sea levels are rising. Satellite measurements since 1992 show sea levels are rising at 3.2mm/year, which is 50% faster than the average rate of sea level rise of the 20th
- NASA reports that Arctic sea ice is melting rapidly. In fact, the minimum sea ice (in September) is declining at a rate of 13.3% per decade.
- In a warming climate, you’d also think that land ice sheets in Greenland and Antarctica would shrink. NASA reports that there have been significant losses of ice from the Greenland and Antarctic land ice sheets. Greenland has lost over 3,500 gigatonnes of ice since 2002 at a rate of about 280 gigatonnes per year. Melting land ice raises sea levels.
- A warmer planet would see glaciers melting at higher rates. The World Glacier Monitoring Service has shown that glaciers have lost almost 20 metres of water equivalent since 1980. In data that runs through until 2015, the year of greatest glacier losses was 2003. The second greatest was 2015.
- More ice melting means that the ocean becomes less salty. That, in turn, is predicted to slow down the Atlantic Meridional Overturning Circulation (AMOC) – of which the Gulf Stream is an important part. If the AMOC stops or slows, then Europe is predicted to suffer significant freezing events. Researchers report that the AMOC has been slowing over the decade of measurements.
These are actual observed data from credible scientific sources. While I respect Andrew Bolt, Miranda Divine, Donald Trump and Tony Abbott’s right to their opinions and beliefs, I do not think they should be afforded the same scientific credibility as the above sources.
Taking substantive action on climate change requires governments to take it seriously. It requires our Parliaments to properly and diligently weigh the science and the risks.
As always, I welcome your feedback on this, or any other topic on ‘The Tipping Point’.