Climate Change Past, Present and Future

Lecture notes Given at Arizona State University for use at Meetings and Debates|April 2016

by Sir Crispin Tickell


A fundamental point: how do we know what happened in the past?   Do we know what is happening now?   What will happen in the future?

  • Much in the public mind since the conference in Paris in December.   Although widely judged as a success, it left the big questions unresolved:  the role of governments, in particular the United States, and the logic of capitalism as practiced by companies.
  • Climate change is immensely complex, and its effects still more so. They are enmeshed in all the big problems of our time, ranging from human proliferation to loss of biodiversity.   We do our best to cope but the picture changes all the time.   Some people are resolute deniers.   Strangely they include more politicians than ordinary people.

Over millions or thousands of years, the essential elements of climate change are:

  • Natural change:
    • The varying relationship between the Earth and the Sun,the so-called Milankovich effect;  wobble, tilt and spin A good example of what can happen is the drying up of the Sahara – from green forest or savannah to desert –only a few thousand years ago;
    • Variations in atmospheric chemistry, in particular CO2, methane, nitrous oxide, sulphur dioxide and even clouds, and the effects of tectonic plate movement;
    • Occasional climatic catastrophes with profound impacts on society generally (a point often neglected by historians);
    • Volcanic explosions:
      •  Toba 73,000 years ago (affecting the world as a whole);
      • Laki in 1783 (contributing to the French Revolution);
      • Tambora in 1815 (a year of famine without a summer);
      •  El Chichon 1982 (affecting all Central America);
      • Pinatubo 1991 (particularly affecting the United States);
      • Iceland 2014 (upsetting air travel in Europe and elsewhere).
    •  Hits from space, from meteorites, asteroids and other planetary bodies with profound effects on life in general:
      • Chicxulub in Yucatan 65 million years ago (whence the likely end of the dinosaurs, andthe rise of mammals, including you and me);
      •  Barringer Crater in Arizona 49,000 years ago;
      • Tunguska in Siberia in 1908.
  • Human-driven change: Since the beginning of the industrial revolution some 250 years ago, substantial changes have taken place.   Indeed we live in a geological epoch known as the Anthropocene to mark the human impact on the Earth and its living systems.
    • CO2 emissions are now at their highest level in 650,000 years (comparable to conditions 125,000 years ago when the configuration of land and sea was very different): the volume of such emissions has risen from roughly 190 ppm (parts per million) in ice age conditions to 285 ppm in warm interludes to over 400 ppm today (and recently rising by about 2 ppm a year).   As the planet warms, so there is melting of the permafrost, leading to the release of frozen carbon dioxide and methane with effects which haven’t yet been measured. Currently we are adding more than a million tons of carbon dioxide to the atmosphere every hour.
    • Emissions of methane, a twenty times more potent gas than carbon dioxide, has risen from a pre- industrial level of 715 ppb (parts per billion) to 1774 ppb in 2005. Nitrous oxide has likewise increased from a pre-industrial value of around 270 ppb to 319 ppb in 2005.
    • There has been a so far unmeasured increase in black carbon or soot, particularly in Asia (the brown cloud).
    • Likewise warming of the oceans has increased steadily since 1961, and now reaches down to depths of at least 3,000 metres.   Its effects on the atmosphere have a roughly 30 year timelag.   Sea levels are rising by over 3.5cm per decade, and are now accelerating, especially in certain areas such as the East coast of the United States.   Elsewhere melting of the ice may cause land to rise as its weight diminishes.   This can be seen in Iceland, Alaska, Greenland and the Antarctic.   Another effect shows increasing acidification of the surface, affecting all marine life from fish to corals.
    • The latest estimates from the Intergovernmental Panel on Climate Change were published in 2014. More are on their way.   To judge from information now available, there could be a rise in global average temperatures between 2030 and 2060 with wide regional variations.   Most of the warming is so far evident at high latitudes, including the Arctic and the Antarctic, as I have seen for myself.   In land areas North of latitude 45 the summers of 2005, 2007, 2010, 2011 and 2012 were the warmest since 1400.   Since thenhere has been a further rise of 0.69C.
    • There is constant variability everywhere as familiar regularities are upset.   Even the jet streams in theatmosphere are becoming what the Scientific American has called “weird”.   No wonder that some people have described us as a lucky generation in an Earth so far lucky.

The implications of these changes are enormous.   They range from changes in how we value things to changes in specific areas of policy:  in particular energy, and switching away from dependence on fossil fuels (hence the current debate on fracking and its implications);  divestment in fossil fuel companies;  taxation of pollution, and elimination of perverse subsidies;  working out the implications of sea level rise;  increasing demand for fresh water everywhere to meet the needs of a growing population;  better mobilization of the corporate and private sectors, although here companies, in particular insurance companies, are often ahead of governments;  and finding global solutions in a fashion which identifies the national interests of all participating states.   Most of this is desirable anyway, regardless of climate change.


A particular difficulty which arose at the Paris conference was over issues of justice; should the poor and most vulnerable countries suffer most while the rich industrial countries who created the problem suffer least?   By any standards, the world is becoming increasingly hard to manage with some breakdown of the international order.


Even so there is progress on climate change.    People as well as governments are increasingly aware of their vulnerabilities as well as interests.   The threat is clearer than ever.   For many years the broad aim has been to limit global warming to less than 2.0C above pre-industrial levels.   Another has been to set planetary boundaries, in short setting limits which if and when passed would prompt appropriate international action (I add that some have already been passed).   The 28 countries of the European Union have committed themselves to cut emissions to 40% below 1990 levels by 2030;  Mexico was the first so-called developing country to undertake to cut emissions by 22% by 2030;  and in 2013 agreement of a kind was reached by the world’s two top emitters – the United States and China –  to limit their emissions.   On 31 March the United States formalized a pledge to reduce its emissions to 26-28% below 2005 levels by 2025.   Cash is also trickling in for a Green Climate Fund to help poor countries adapt to climate change.   In the financial world there is a corporate green bond market, where money is raised for companies to make environmentally friendly investments.    It is likely to reach over a billion US dollars.   There is also the prospect that if countries breach their commitments they could be liable in international law for the damage they do to others and to the environment generally.


What then needs to be done?

  • In most cases the answers are obvious.   They are local as well as global.   In short we are all directly involved.   If we put the main focus on energy as we should, we must drastically lower emissions of greenhouse gases in whatever form, develop new (and old) sources of energy, set new standards for measuring and coping with carbon emissions, and improve public understanding of the wide and interlocking issues involved.   We must also be ready to cope with catastrophes if and when they occur – as they certainly will – with their myriad implications.
    • So my answer to the question:  What should we do about it?   The answer is a lot;  and it has to be done soon.

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