2010 Diary week 45
Climate Change
Book Review
Below you will find Part 4 of the review of Climate Change: Turning up the Heat by A. Barrie Pittock. These are some snippets: “Today, faster computers enable nearly all climate models to have an interactive ocean, and indeed deep water temperatures are calculated, as are ocean currents.” “The need for truly global simulations at fine spatial scales remains important. Japan has recognized this, and has built the Earth Simulator supercomputer, capable of modeling the climate at fine scales for the whole globe. It contains the equivalent of many hundreds of ordinary supercomputers (circa 2004), and currently is running a climate model with 100 levels and a horizontal resolution of 10 kilometers, compared to most AOGCMs that have a resolution of 100 or more kilometers. So far they have only carried out simulations.” “Projecting the future is an everyday procedure for providing insight into what may happen. It forms the basis of many decisions about what to do. In relation to climate it is made more difficult by the complexity of the climate system, the long time-scales and the possible human influences on climate through future human behaviour.” “These contrarians say that if such changes happened naturally in the past, why should any changes occurring now be due to human influence? Or else they argue that, since life survived such changes in the past, it will survive similar changes in the future, so why worry about it?” “While natural climate change has happened before and can happen again, this does not rule out the simultaneous occurrence of human-induced climate change. Moreover, human-induced climate change may be more immediate and rapid than past changes, and it would happen at a time when there are an unprecedented six billion human beings alive on Earth. Considering the consequences to such a human population if it had existed during the last glacial cycle should dispel any equanimity about the consequences of imminent rapid climate change.”
CLIMATE CHANGE
TURNING UP THE HEAT
A. BARRIE PITTOCK
EARTHSCA/CSIRO PUBLISHING 2005
PART IV
Chapter 3: Projecting the Future (continued)
Forecasting the weather
• Foresight is routinely used in regard to the weather, and affects many of our day-to-day decisions. It is therefore useful to compare the basis for weather forecasting with that for climate projections, in order to understand both what they have in common and what the differences are.
Why climate projections are different
• There are two main differences:
First, climate projections are not about predicting the exact weather at any time in the future, but rather about projecting the statistics (average behaviour and variability) of the future weather. This reduces the relevance of short-term chaotic behaviour in the atmosphere.
Second, because climate projections are about the statistics of weather many months, years or even centuries into the future, much slower influences on the weather or climate must be taken into account.
How good are climate models
• Today, faster computers enable nearly all climate models to have an interactive ocean, and indeed deep water temperatures are calculated, as are ocean currents.
• A range of different types of climate models are available, and various names or abbreviations are used to indicate differences in their complexity.
• Climate models have been tested and improved quite systematically over time.
• The need for truly global simulations at fine spatial scales remains important. Japan has recognized this, and has built the Earth Simulator supercomputer, capable of modeling the climate at fine scales for the whole globe. It contains the equivalent of many hundreds of ordinary supercomputers (circa 2004), and currently is running a climate model with 100 levels and a horizontal resolution of 10 kilometers, compared to most AOGCMs that have a resolution of 100 or more kilometers. So far they have only carried out simulations.
• Overall, model performance and verification is complex, but is being actively tested and improved. Climate models provide projections that are far more sophisticated and reliable than simple extrapolations from observed climate trends.
The state of climate projections
• Projecting the future is an everyday procedure for providing insight into what may happen. It forms the basis of many decisions about what to do. In relation to climate it is made more difficult by the complexity of the climate system, the long time-scales and the possible human influences on climate through future human behaviour.
Chapter 4: Uncertainty is Inevitable, But Risk is Certain
Despite uncertainties, decisions have to be made
• Contrary to a widely held belief, no measurement of a continuous quantity is absolutely exact. Nothing is absolutely certain in science. There are many circumstances where a less exacting standard of certainty is sufficient to find a proposition, prediction or theory useful.
• The design standard set for a bridge or dam ensures that it will not collapse because failure would be catastrophic. Weather forecasts are useful even if the chances of their being wrong are 1 in 10 or even 1 in 3 because the consequences of not taking an umbrella are not disastrous.
• To a farmer acting on seasonal rainfall forecasts on how much to plant, two good harvests in three may well make up for a crop failure one year in three.
• Tropical cyclones landing on the coast are serious and it is prudent to take precautions even if we are only near the possible path of a tropical cyclone. Most of us insure our house against loss by fire, even though we believe that it is very unlikely that our house will burn down.
Uncertainty in climate change projections
• In any estimates of future climate change there are a number of sources of uncertainty. Some of these arise from the science itself, and some from uncertainty about future human behaviour – especially future emissions of greenhouse gases. These two major sources of uncertainty each account for about half of the total uncertainty.
• This is fortunate, since it means that, despite the total uncertainty, different assumptions about future human behaviour can be used to test the effect of such behaviour on climate. This can give us useful information about what sort of human behaviour is desirable to avoid the worst possible climate changes. In other words, it is useful for developing policy.
• The important thing with all these uncertainties is that we should be aware of them and take them into account, both in our own estimates, and in assessing those of others. We should examine assessments to see how clearly (or transparently) they state assumptions and uncertainties.
• Further we should not regard results as of no use at all if they have large uncertainties attached to them – after all, admitted uncertainty implies a degree of understanding and honesty, and such results still limit the possibilities.
• The most likely results are probably somewhere near the middle of the range of uncertainty, unless the study is biased by its assumptions.
• Some knowledge is better than none, provided we use it wisely in full awareness of its limitations. Obviously, where uncertainties are large we should try to reduce them, but in the mean time we need to make the best of what we have to guide both adaptation and mitigation policy.
• When it comes to estimating how uncertain projections of future climate change and climate change impacts may be, we need to distinguish between two types of uncertainty.
• One is the uncertainty about something that can be measured repeatedly. This can in principle be reduced by taking more measurements.
• The other sort of uncertainty arises when there cannot be repeated measurements. This is usually because we are dealing with some prediction of the future based on a theory or model, often with assumptions about future behaviour or influences.
• People working on climate impacts, including the scientists and policy advisors associated with the Intergovernmental Panel on Climate Change (IPCC), have only recently started to come to grips with this complex problem, and there was a new emphasis on quantifying uncertainty in the IPCC’s Third Assessment Report in 2001. Thus, many of the estimates of uncertainty given in this book are preliminary, and may not cover the full range of uncertainty in some cases. In particular, there may be unexpected developments and ‘surprises’, which may well lead to larger, as well as smaller, climate changes and impacts.
From polarization to probability and risk
• People respond in different ways to uncertainty. Sometimes they get confused and see it as a reason for concluding that they know nothing useful on the subject, and therefore see no reason to act. This is especially the case if action would have obvious costs, and it is the position taken by many who challenge the reality of human-induced climate change.
• These people in denial tend to focus on the uncertainties rather than on what is known. Some (but not all) may have a vested interest (financial or ideological) in doing nothing, and use the uncertainty as an excuse for delaying meaningful action.
• In other situations, however, people may conclude that although there is uncertainty, it is worth taking a gamble and doing something even if the odds are only marginally favorable. Farmers do this as part of their everyday coping with the uncertainties of the weather.
• How we react to uncertainty depends in large part on how well we understand the odds, and on what is at stake. It is not only the probability that matters, but also the consequences. It is not a matter of the accuracy of a particular prediction, but of the probability of a range of outcomes with serious consequences.
• A likely outcome having large consequences is a large risk, while a small probability of a low-consequence outcome is a small risk.
• In the case of climate change, natural and human systems have been forced by past natural climate variability to evolve or adapt so that most of the time they operate within a ‘comfortable’ range in which they operate well. Sometimes systems exist outside that range in climatic conditions in which they survive, but not well. This is sometimes called the ‘coping range’.
• Occasionally natural and human systems experience extreme climatic events that are damaging, sometimes fatally. These events are called ‘natural disasters’ and include droughts, floods, storm surges and wildfires.
• Climate change moves the average climate so that comfortable conditions become less common, and extreme events, which can be defined as those falling outside the previous coping range, become more common or of greater severity.
• What is of concern in climate change is therefore the risk associated with changes that take us more frequently into more extreme conditions that are damaging or disastrous. What we are concerned about is the risk of changes that take us above the threshold of these extremes.
• The probability of exceeding a particular impact threshold of, say, temperature or rainfall at some time in the future can be determined more confidently than the probability that the temperature or rainfall will have a particular value at that time.
• To understand why this is so, we need to know what a probability distribution is, and what it looks like. This is the way in which the probability of a particular variable having a particular value varies with the value of the variable.
Estimating risk
• The IPCC, in its report in 2001, was reluctant to attach probabilities to particular magnitudes of warmings within the large range of 1.4 to 5.8°C that it estimated for the year 2100. This was due to the great difficulty of assigning probabilities to the relevant population, socio-economic and technological factors that would determine greenhouse gas emissions decades ahead.
• This difficulty was accentuated by the likely influence of future policies on these factors that determine emissions.
• The lack of probability estimates presents problems in developing policy for reducing greenhouse gas emissions and in planning for adaptation to climate changes. Decision-makers need to base decisions on some risk assessment both in mitigation and adaptation policies, since such policies involve costs.
• The central objective must be to avoid concentrations of greenhouse gases that may lead to ‘dangerous interference with the climate system’. Therefore, developing appropriate mitigation policy requires an understanding not only of the impacts of any given concentration of greenhouse gases in the atmosphere (which has a range of uncertainty), but also of the likelihood of reaching a critical level of greenhouse gas concentrations (a dangerous threshold) at some time in the future.
• The urgency and severity of any mitigation measures needed to avoid reaching a critical threshold depends on the risk (probability multiplied by consequences) of what may happen if such measures are not taken.
• Risk cannot be managed or treated efficiently unless it is properly assessed. This requires an estimate of both the probability of an event occurring and an assessment of its consequences.
• The risk of exceeding some critical level of consequences (defined by collective global value judgements in the case of the UNFCCC) is central to deciding the urgency and extent of reduction in greenhouse gas emissions (that is, mitigation) that is needed.
Uncertainty and the role of skeptics
• Genuine questioning and skepticism in science is good: it is one of the ways that science progresses, leading to the critical examination of assumptions and conclusions, and eventually the substitution of newer and more reliable theories for older ones that are less robust.
• This is the scientific method of hypothesis testing and development of new paradigms. However, challengers need to apply their critical faculties to both sides of an argument, and to admit uncertainties that may work for or against any particular proposition.
• The devil’s advocate position is legitimate in a purely scientific debate, where there is plenty of time for contending arguments to be put and an eventual decision reached by the scientific community as a whole. However, where critical policy issues or urgent decisions are at stake, responsible scientists will give balanced advice, admitting any uncertainties on either side of the debate.
• The conclusions from the IPCC have always been subject to uncertainty, always subject to revision, and as the science has progressed the conclusions have been expressed more and more explicitly in terms of estimated ranges and probabilities.
• A number of people have emerged who deny there is significant human-induced global warming and treat science like a debate in which they apparently see their job as to selectively use any possible argument against a proposition to which they are opposed, instead of looking at the balance of evidence.
• In a debate affecting world affairs, economies and human welfare, debate should be responsibly directed at finding the balance of evidence, the testing of all statements, and the free admittance of all doubts and uncertainties, whether they favour a particular proposition or not.
• In this context, one-sided challengers should more accurately be labeled ‘contrarians’ rather than skeptics, since they are skeptical of one position but do not also question the contrary.
• It is invidious to ascribe motives to particular individuals, and in most cases I will not do that here. However, we can think of a number of possible underlying positions or interests, related to the enhanced greenhouse effect and its impacts, which may motivate the positions held and arguments used by some contrarians.
• One such prejudice comes from people, often scientists in disciplines other than climatology, who are not convinced of the value of predictive modeling in the physical and mathematical sciences.
• Another question raised by some contrarians comes from those familiar with the geological and other paleo-evidence of past natural changes in climate, which clearly were large, and not the result of human influence.
• These contrarians say that if such changes happened naturally in the past, why should any changes occurring now be due to human influence? Or else they argue that, since life survived such changes in the past, it will survive similar changes in the future, so why worry about it?
• While natural climate change has happened before and can happen again, this does not rule out the simultaneous occurrence of human-induced climate change. Moreover, human-induced climate change may be more immediate and rapid than past changes, and it would happen at a time when there are an unprecedented six billion human beings alive on Earth. Considering the consequences to such a human population if it had existed during the last glacial cycle should dispel any equanimity about the consequences of imminent rapid climate change.
• Another class of contrarians is those who are driven by economic and political judgements. A case in point is the best-selling book The Skeptical Environmentalist by the Danish statistician Bjørn Lomberg, whose reasoning is quite explicit.
• Lomberg takes the position that many environmental issues have been exaggerated and proceeds to produce statistics pointing to environmental improvements in recent decades (many the result of agitation by the environmental movement).
• Considering the enhanced greenhouse effect, Lomberg, while tending to downplay the risks from climate change, concedes that it is a reality. His argument is not that human-induced climate change is not happening, but rather that it is manageable, and that reducing greenhouse gas emissions would be prohibitively expensive.
• This is a value judgement based on discounting the more severe possible impacts, technological optimism regarding our adaptive capacity, and technological pessimism regarding our ability to reduce greenhouse gas emissions at low cost.
• He argues that other issues such as world hunger and water supplies are more important than climate change, but fails to recognize how climate change impacts on these issues. These matters are discussed in Chapters 6 (impacts), 7 (adaptation), 8 (mitigation) and 9 (climate change in context).
• Some contrarians are deeply suspicious of the motives and integrity of climate scientists. They especially suspect the IPCC as deeply biased and flawed and accuse it of censoring or doctoring its reports. This is quite contrary to the rigorous open reviews and other procedures adopted by the IPCC to safeguard against bias, and the fact that its reports have to be approved by a whole range of governments with many different views and interests.
• Beyond all these possible motivations for prejudice are those who have a real or perceived economic interest in denying that human-induced climate change is a reality. Some of these genuinely believe the enhanced greenhouse effect is not so, while others fail to see any urgency to delay action for their own (and possible others’) economic benefit.
• The public perception of the debate over climate change is shaped by the media’s adherence to a doctrine of ‘balanced reporting’. This tends to give equal space to the considered judgements of the scientific community, expressed in peer-reviewed publications such as the IPCC reports, and the often completely un-refereed opinions or advocacy of a contrarian minority.
• There has been a media tendency for giving equal space to unequal scientific arguments, which often misrepresents the balance of evidence and plays into the hands of vested interests opposed to any real action to limit climate change.
• Peer review is not perfect and does not guarantee correctness. It is just the first stage: a hypothesis or argument that survives the first test is still subject to further testing by other scientists. However, peer-reviewed papers and reports can be considered to be more than an opinion, and should not be lightly dismissed in favour of untested opinions.
• An awareness of the peer-review system and the sources of information can help the media, the public and decision-makers to distinguish between arguments derived from well-based scientific judgements and those arising from un-checked personal opinions.
Application of the ‘precautionary principle’
• Uncertainty in regard to the rate and magnitude of climate change, and in relation to its effects, operates in both directions: it can mean that effects may be less than current best estimates, or more. This raises the problem, common to most human endeavours, of how to make decisions in the face of uncertainty. This is even more acute, in the case of climate change, because decisions made now may determine consequences many decades into the future.
• The Precautionary Principle, as included in the Rio Declaration at the Earth Summit in June 1992, and assented to by representatives of most of the nations of the world, states
Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.
• This principle has been incorporated into many environmental agreements and regulatory regimes, including Article 3 of the UNFCCC, where it is expressed as follows
The parties should take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate against its adverse effects. Where there are threats of serious or irreversible damage, lack of full certainty should not be used as a reason for postponing such measures, taking into account that polices and measures to deal with climate change should be cost-effective so as to ensure global benefits at the lowest possible cost.
• This is the type of reasoning that has long governed engineering design, safety regulations, the insurance industry, foreign policy and military planning. It is normal to consider worst case scenarios and to consider what action is appropriate either to avoid such scenarios coming to fruition, or to deal with them if they do occur.
• This leads to two key questions: what counts as serious environmental damage that should be avoided, and what measures are justified as reasonable and cost-effective responses? The answers to these questions are really what successive IPCC reports, and the UNFCCC are all about: they are complex and multi-faceted, combining scientific information and human values.
• Differing human values and different self-interests will inevitably lead to controversy, debate, and the exercise of political power in deciding what action is actually taken by governments, businesses and ordinary people.
• In what follows, this book will explore the above questions, with a view to suggesting what a creative and adaptive policy response might entail, and how we might help it along.