Climate Change

Some facts on Climate Change

  • Greenhouse gases such as CO2 trap some of the outgoing heat (infrared radiation) from the Earth, and so keep us warmer than we would otherwise be, just like a blanket.

  • The effect is large. It is estimated that without the atmosphere, the average global temperature would be minus 18 degrees Celsius, about 32 degrees colder than now.

  • By adding CO2 to the atmosphere, all other things being equal, the average temperature must go up – it’s simple cause and effect, just like adding a blanket to your bed. How much will it go up? It is difficult to calculate because, for example, temperature affects the area covered by ice and clouds, which in turn affects temperature. So we must ask the experts. The latest IPCC Report estimates that a doubling in the CO2 concentration to 560 parts per million will cause a temperature rise of about 3 degrees Celsius.

  • Global CO2 emissions from burning fossil fuels are 28 Gigatonnes per year, equivalent to about 5 parts per million of extra atmospheric CO2 per year.





                                                                                                                      Figure 1


  • A picture is worth a thousand words. Figure 1 shows the concentration of CO2 in the atmosphere as a function of time. Note the variation with the seasons, superimposed on a steady rise. It has risen from 280 parts per million in the pre-industrial age to over 400 ppm now. This is due to our burning of fossil fuels. In fact, about half our emissions seem to have been absorbed by the oceans or vegetation. This has already earned us a temperature rise of about 1.3 degrees Celsius, but not all of that has appeared so far, delayed by the heat sink effect of the oceans.


















Figure 2


  • Figure 2 shows a measure of the global average temperature, relative to the period 1951-1980, as a function of time. There are quite large fluctuations year to year, but any stock market analyst will tell you the trend for the last forty years is upwards. The total rise in temperature since the pre-industrial era is about 1.0 degrees.

  • Much has been made of the ‘pause’ between the anomalous peak year of 1998 and (say) 2013, but that has now ended. Similar ‘pauses’ may be seen between 1981-1993, or 1973-1985. The data remain within the ‘tramtracks’ established over the past four decades.

  • If nothing is done, the temperature rise by the year 2100 is predicted to be between 3 and 7 degrees Celsius, according to the IPCC Report.

  •  Australian total greenhouse emissions were equivalent to around 29 metric tonnes of CO2 per head per year in the reference year 2005. This was one of the highest in the world, more than four times the global average.

  •  Figure 3 shows Australian total greenhouse emissions in tonnes of CO2 equivalent per head as a function of time. They at last began to turn downwards in 2007, but there is still a great deal to be done. To satisfy the Paris agreement, we will need to get down to about 15 tonnes per head by 2030, versus 22 tonnes today.






















Figure 3. Australian emissions (metric tonnes of CO2 equivalent per capita) versus year (blue curve) [Source: Dept. of the Environment and Energy]

For further information, see the 5th IPCC Report (2013) and/or the Australian Academy of Science Report, “The Science of Climate Change: Questions and Answers”.


A word about the climate sceptics: There has been an extraordinary campaign by some people and some sections of the media to try and discredit the climate scientists and throw doubt on their findings. You will be wary of those with vested interests. The campaign to discredit climate scientists bears an eerie similarity to the decades-long campaign by big tobacco to discredit health professionals over the dangers of smoking. The tactic is to sow doubt. In this case, it’s the oil companies like Exxon-Mobil and the big coal miners who have funded the obfuscation campaign, e.g. through bodies like the Heartland Institute in the US. See “Merchants of Doubt”, by N. Oreskes and E. Conway (Bloomsbury, 2011).



International Agreements

The world was first alerted to the problem of climate change by scientists such as James Hansen at NASA, although the chemist Arrhenius had made a first calculation of the effect a century earlier. The first response of the international community was the United Nations Framework Convention on Climate Change (UNFCCC), an international environmental treaty negotiated at the Earth Summit in Rio de Janeiro in 1992. The UNFCCC objective was to "stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system". In 1997, the Kyoto Protocol was concluded, and established legally binding obligations for developed countries to reduce their greenhouse gas emissions in the period 2008-2012.

In 2015 the Paris Agreement was adopted, governing emission reductions from 2020 on through commitments of countries in ambitious Nationally Determined Contributions. It aimed at limiting global warming to less than two degrees Celsius, and to pursue efforts to limit the rise to 1.5 degrees Celsius. The Paris Agreement was signed in 2016 and was to enter into force upon ratification by 55 countries representing over 55% of greenhouse gas emissions. As of February 2020, all UNFCCC members have signed the agreement, 189 have become party to it, and the only significant emitters which are not parties are Iran and Turkey (and recently, the US!).

It must be noted that the Paris agreement carries no binding commitments on individual countries as to their own emissions, and it will rely on the good will of all parties to be effective. It is already apparent that the target of 1.5 degrees is unachievable, and was included largely as a sop to the small island states that are liable to be submerged by rising sea levels. All countries must cooperate together effectively if we are to have any chance of halting the temperature rise at acceptable levels.

Recently both the US and Australia have been dragging their heels on this vital issue. In June 2017, U.S. President Donald Trump announced his intention to withdraw the United States from the agreement. Under the agreement, the earliest effective date of withdrawal for the U.S. is November 2020, shortly before the end of President Trump's 2016 term. In practice, changes in United States policy that are contrary to the Paris Agreement have already been put in place. Australia has announced that it will meet its target, but only by including large carry-over credits from the previous Kyoto agreement, which all but three other countries have declared inadmissable.


Our association will try to ensure that Australia meets or exceeds its targets under the Paris Agreement. For several years we have sent an open letter to all Federal MPs in Australia, urging effective action on climate change. The most recent letter follows.



Open Letter to MPs concerning climate change (March 16, 2017) - extract

We were very pleased that Australia signed up to the Paris Agreement on climate change in 2015. This is obviously an issue where the world’s nations need to work together if we are to achieve anything. Under the Paris agreement, the world’s nations have agreed to work together to try and limit global warming to 2 degrees Celsius. It is extremely important that Australia should live up to its commitment, as an influential middle-ranking member of the world community of nations, even if the US should resile from its commitment. We are all in this together.


I enclose our ‘fact sheet’ on climate change, as a reminder. Note that the so-called “pause” in global temperature from 1998 -2013 has now ended, and the average temperature in the past three years has climbed rapidly back to the top of the “tram tracks” established over the past fifty years. The year 2016 was the hottest year ever recorded. Unfortunately, the levels of carbon dioxide in the atmosphere are still climbing rapidly also, and show no sign of levelling out. We have a great deal still to do.


It is obvious that this problem can only be tackled by collective global action. Once again, we call upon the Parliament and the government to establish and maintain a leading position for Australia in the fight against climate change. As one of the richest countries in the world, and with one of the highest emissions of carbon dioxide per person in the world, we have a moral responsibility to lead the way towards a solution to this problem. Furthermore, as the oldest and driest continent on the planet, Australia is likely to suffer some of the worst effects from climate change, and simple prudence demands that we do something about it.


We endorse the statements from Australia's Chief Scientist and the Australian Academy of Science concerning the need for urgent action by Australia and all other nations to decrease carbon emissions substantially and rapidly. This issue is above politics – it is a question about the world we shall leave to our children. We have procrastinated too long on this issue.


Australia has announced a target of decreasing our carbon emissions by 26-28% over 2005 levels by 2030. When our expected increase in population is taken into account, the target is equivalent to a decrease in carbon emissions per head of population of about 50%, one of the highest in the developed world. This is going to be difficult enough to achieve, although we have made a good start.


Equity demands that any new global compact looking out to 2050 should aim at the same, lower level of greenhouse emissions per head by 2050 from all countries, developed or not. This will provide a major challenge for a big emitter like Australia, but surely we have the wealth and the expertise to meet such a challenge.


We should begin with the ‘low-hanging fruit’. A solar hot-water heater, preferably with gas booster, will save the average household large amounts of energy and carbon emissions, and save a considerable amount of money as well. Therefore we suggest that:

  • Solar hot-water heaters be made compulsory for all new houses;

  • A loans scheme should be established to retrofit solar hot-water heaters to all existing houses. Such a scheme would be highly advantageous from every point of view.  


We also advocate adherence to the European emissions trading scheme. This would link us to the most progressive and responsible group of nations on this topic, and introduce a market-based mechanism at a very much cheaper rate (presently) than the old carbon tax.


This is an issue which has major repercussions for our descendants and the future of the planet generally. Australia must play a serious and constructive role in its resolution.


Yours sincerely,


A/Prof Chris Hamer

President, Scientists for Global Responsibility (Australia)

Updated September 2020

Image Source:

© 2016 by Rafia Hussain. Proudly created with

  • Facebook Basic Black
  • LinkedIn Basic Black
  • Twitter Basic Black