Thursday, 28 February 2013


“As human beings, we are vulnerable to confusing the unprecedented with the improbable. In our everyday experience, if something has never happened before, we are generally safe in assuming it is not going to happen in the future, but the exceptions can kill you and climate change is one of those exceptions.” - Al Gore

It’s official! Australia has experienced its hottest Summer on record. Average temperatures beat the record set in the summer of 1997-98, and daytime maximum temperatures knocked over the 1982-83 record. January 2013 has been the hottest month since records began in 1910. Our climate is changing and we now have the weather records to prove it.

Climate is a statistical description of weather. It describes the average weather experienced over a period of time, over either a single location, or averaged over a large region. Climate also describes how variable the weather is around those averages. Climate also describes trends: Longer-term changes in weather that are distinct from the shorter-term variability.

When it comes to climate change, there is often confusion as to when one should consider a particular meteorological event to be “just weather” or something more significant in a climatological context. Individual weather and climate events that scientists consider most significant are those that are both at the extremes of our historical experience, and consistent with quantifiable trends.

September 2012 to February 2013 were warmer than the previous high for that period, set in 2006-2007. Average summer temperatures across Australia were 1.1°C above the 1961-1990 average, surpassing the previous record, set in 1997-98, by more than 0.1°C. Daytime maximum temperatures also set a record; they were 1.4°C above normal, and 0.2°C above the 1982-83 record. And the most significant thing about all of these extremes is they fit with a well established trend in Australia, that is it’s getting hotter, and record heat is happening more often.

Australia has warmed by nearly a degree Celsius since 1910. This is consistent with warming observed in the global atmosphere and oceans. Over the next century, the world will likely warm by a further 2 to 5 degrees, depending on the amount of greenhouse gases emitted into the atmosphere. Under mid-to-high emissions scenarios, summers like this one will likely become average in 40 years time. By the end of the 21st century, the record summer of 2013 will likely sit at the very cooler end of normal.

An interesting feature of the heat this summer is that it occurred during a “neutral” period in the El Niño-Southern Oscillation (that is, it was neither La Niña nor El Niño). Up until this year, six of the eight warmest summers, and the hottest three summers on record, occurred during El Niño years. This essentially means that the record was consistent with warming trends, and achieved without an extra push from natural variability associated with El Niño.

The oceans surrounding Australia have also been exceptionally warm. January 2013 was the second warmest on record, following an unusually hot 2012, and a record hot 2011 for Australian-region sea surface temperatures. These temperatures are measured very differently to air temperatures over land.

Apart from the heat, the summer of 2012-13 will be notable for rain and floods along the east coast, especially those which fell in late January as the remnants of Tropical Cyclone Oswald tracked south just inland from the coasts of Queensland and northern New South Wales, bringing heavy rains along the length of its track. A second round of heavy rain occurred in southeast Queensland and coastal New South Wales in the last week of February. The late January rainfalls were significant and led to major flooding in numerous rivers, especially the Burnett, which reached record levels after a one-day catchment-average rainfall which was nearly 70% above the previous record.

December 2012 was the hottest December on record for Southern Hemisphere land areas, and January 2013 was the hottest January. Australia was a large contributor to this, but so were southern South America and southern Africa. Many parts of southern Africa had their hottest January on record, while the month was also much hotter than normal in large parts of Argentina, Chile and Brazil. In parts of Patagonia, January temperatures were more than 4°C above normal.

We have to get used to records like this being broken as our climate changes worldwide. A few degrees up or down may not sound like much, but repeated small increases have a cumulative effect with many consequences on a global scale. Humans have relative little power to deal with weather at the best of times and where climate is concerned we have even less power. Global warming may be the problem presently, but it only takes a major volcanic explosion with much ash ejected into the atmosphere to have a very real effect on climate for many years – in this case a cooling effect.

“Following the huge eruption of Krakatoa in 1883, enough reflective volcanic aerosols were ejected into the atmosphere that the following year was known as the year without a summer.  But the effects of that debris have been much longer-lived.  According to the report in ‘Nature’ this week, the volcanic-induced cooling of the oceans caused by Krakatoa's eruption lasted almost a century, enough to offset a large amount of anthropogenic rises in ocean temperature and sea level.  In plain English, were it not for Krakatoa going boom all those years ago, we'd be in a worse state currently than we are.” (Jonathan M Gitlin, Feb 10 2006).

Whether we modify our behaviour that may be instrumental in climate change or not, there are forces of nature at play on our planet that demonstrate to us that we humans are puny and impotent. What we must do is act wisely, take care of our environment in the best way we can and hope for the best in terms of natural events that we have no control over…

1 comment:

  1. Alas we really do have to get used to records like this being broken each year! And, I would add, a few degrees up sounds truly ominous, given the changes to sea levels, bush fires, cyclones etc.

    The worst aspect seems to be the reduction of drinking water. If there is a world war in the future, it will be over water and not petrol.