EXPERT REACTION:Bureau of Meteorology releases Annual Climate Statement 2015

2015 resulted in Australia’s 5^th hottest year on record. This follows Australia’s 3^rd hottest year on record in 2014 and our hottest year on record in 2013. All of our 10 hottest years have occurred since 1998. Much of the excess heat occurred towards the end of the year, where similar to 2013 and 2014, a swathe of spring temperature records were broken across the country. In 2015, this included our hottest October on record nationally. In terms of natural climate variability, one of the strongest El Nino’s on record, coupled with activity in the Indian Ocean helped drive these high temperatures towards the end of the year. Larger temperature increases during the shoulder seasons is also consistent with anthropogenic climate change. Thus, the extreme heat Australian heat experienced in 2015, especially during the last four months, is a result of both natural variability of the climate and human influence on the climate system.

Two factors dominated Australia’s climate of 2015, a strong El Niño and human-caused global warming,  as well as normal natural variability. The strong El Niño was due to much hotter than normal ocean temperatures in the central equatorial Pacific in the second half of the year. This led to reduced rainfall across much of eastern and southern Australia in winter and spring, and hotter temperatures.

In addition to El Niño, human-caused climate change was a major contributor to the high temperatures across Australia in 2015. Global warming has added about one degree Celsius to temperatures across Australia over the last 60 years, increasing the frequency and intensity of heat waves that occurred across much of southern and eastern Australia in spring and in December. These dry and hot conditions have affected farmers, led to a rapid decline in water resources and contributed to severe bushfire weather early in the fire season.

While El Niño conditions are likely to wane in autumn and return more normal rainfall to eastern Australia, global warming will continue to increase the frequency and intensity of heat waves across Australia for many decades.

2015 has seen the globe record its warmest year since records began, and it’s been warm in Australia as well. Overall, it was Australia's fifth-warmest year on record.
 
The year was dominated by the influence of an El Niño event which typically leads to warm and dry conditions across Australia, particularly the eastern half of the country.  The El Niño became established during May and strengthened to become the strongest event in the past two decades. The year ended on a very hot and dry note as the influence of El Niño took hold in September.
 
Rainfall across Australia was below average. While various parts of the country received some rainfall - most notably, New South Wales and inland Western Australia - fed by moisture of a record-warm Indian Ocean during winter, rainfall was well below average elsewhere in the country. Drought conditions persisted through inland Queensland, southwest Western Australia and the southeast, including Tasmania.

The BoM annual climate statement provides a wealth of detailed data on our climate in 2015. These data are best viewed in the context of the much longer term trends that they are part of, continuing the multi-decadal trend of a warming continent with periods of record-breaking heat, such as October last year. Perhaps most striking in the statement is the long-term trend of global mean temperature, where 2015 is very likely to be the warmest since records began in 1880, and by a very large margin.

Global warming is back on the urgent list. Expect an Emissions Trading Scheme (ETS) 

Based on preliminary data, the estimated global mean temperature for 2015 was the highest on record “by a substantial margin”. It was also the year of the highest concentration of CO2. These two facts reinforce the need for strong policy measures in all countries to reduce the level of greenhouse gas emissions.  Such policies will encourage a switch to non-polluting technologies for electricity generation and industrial production.

This raises the question of how to achieve the implied stricter greenhouse gas emission targets.

Current Australian government policy, direct action, is only a short-term compromise. You can, in theory, restrict emissions under any of the policy alternatives. The difficulty with direct action, used alone, is that it quickly becomes costly to tighten the emissions target, and it gets restrictive in terms of the amount of government involvement necessary. The Liberal-National government is unlikely to support such a policy scenario.

Most economic analysis shows that an emissions trading scheme (ETS) is the most efficient, least-cost policy, so that economic pressure will encourage its adoption. Also, an ETS is the international standard. Every country that is seriously tackling carbon emissions has an ETS. Moreover, it would be counterproductive for Australia not to be a full participant in the international carbon market.

Having said that, in reality, policy to reduce greenhouse gases will be an amalgam of various policies, as it is in Europe, where an ETS is the principal policy, but where some elements of direct action also exist in the form of incentives to firms to adopt non-polluting technology.

Conclusion: Expect an emissions trading scheme in Australia as early as 2017, no matter which party forms government after the next Federal election.

The evidence clearly shows the oceans are continuing to warm.  The oceans absorb over 90 per cent of the heat accumulating in the climate system. 
 
The evidence also indicates that sea level is continuing to rise. This rise is from expansion of the warming ocean and the loss of mass from glaciers and ice sheets, with a small contribution from changes in land water storage.
 
The rate of rise over the last two decades is faster than for the 20th Century as a whole.  Of major concern is the apparent increase in the rate of mass loss from the ice sheets, particularly surface melting in Greenland and glacier outflow in West Antarctica.