Platform users were asked to submit their own questions around climate change ahead of the UN Climate Change Conference being held in Copenhagen this month.
Six questions were chosen and answers will be supplied by the OU’s academic experts. Here’s the response to the first question…
How do we know that climate change is real and we’re not just experiencing a weather cycle?
By Prof Robert A. Spicer (pictured above)
We know that climate has changed significantly in the past. Pictured above is a scene 70 million years ago very close to the ancient North Pole (83 degrees north palaeolatitude). Instead of ice, lush forests supporting a diversity of animals such as dinosaurs, mammals, fish, birds, insects and even marsupials grew in profusion. Evidence for this is in the form of fossilised trees and bones and unambiguously tells us of past warmth. Other geological evidence shows that without ice caps sea levels were at least 70 metres higher than now. Rather that arguing over "wiggles" the geological record shows what our planet is capable of with carbon dioxide levels likely to be reached within just a couple of human generations.
This is where you cannot just look at what has happened in the recent past but you have to take the long view. A combination of direct measurements from the air and from ice cores all show that greenhouse gas concentrations in the atmosphere (excluding water vapour which doesn't stay in the atmosphere very long) taken together and expressed in terms of carbon dioxide equivalents, are now higher than anything the world has seen for over 20 million years. We have gone from pre industrial levels that stayed more or less constant for thousands of years to our present "off the scale" values in less than 300 years. When we have seen similar natural increases in greenhouse gases in the past (but sudden pulses rather than sustained emissions), the average surface air temperature of the Earth has risen by around 5°C and it took over 100,000 years for the Earth system to go back to where it was before the increase. These are based on actual measurements of the real Earth and not computer models. Moreover, the basic physics of the greenhouse effect has been known for over a hundred years and as far as I know humans cannot change the laws of physics.
The consequences of climate change at the pace we know it is taking place (irrespective of the cause) is frightening. As someone who has studied past climate change for over 30 years (I started looking at past Arctic climates long before it became "fashionable"), the present state of affairs worries me. It is deeply concerning because, in my view, change is now inevitable and that change is likely to be far more severe and quicker than anything predicted by the IPCC, largely because the climate models are based on weather forecasting and are inherently conservative. The models cannot, for instance, reproduce what we see evidence for in the geological past no matter how we reconfigure them with.
It isn't that our species cannot biologically cope with warmth, after all with the right equipment we can dive into the deep ocean and even live in space. The reason why we are so vulnerable is that our social, political and social structures are built around assumptions of stasis (national boundaries are fixed, we assume that coastlines stay in roughly the same place because sea level stays the same, food and water are available). If any of these basic resources change then human history shows the result tends to be conflict.
We have a very narrow window of opportunity for global politics to show we can manage our planet effectively. Rather than squabble over who's "fault" climate change is we should realise we have a communal job in hand to manage that change, natural or human induced, in order to avoid climate driven resource change, migration, and conflict.
By David Humphreys, Senior Lecturer in Environmental Policy
First, it is necessary to differentiate between climate and weather. Even if the world’s climatic system was completely stable with no increase or decrease over time in the mean global temperature, there would still be movements of energy, wind and water within that system, i.e. weather. People who ask “How can we predict climate change for the next century when we don’t even know if it will rain next week?” have failed to understand the difference between climate and weather.
What seems to underlie this question is whether recent climate change is “natural” or the result of anthropogenic emissions of greenhouse gasses since the start of the Industrial Revolution some 250 years ago. It is often asked “Given that the Earth’s climate has always changed, how can we be sure that recent changes are anthropogenic?”. While it is true that the Earth’s climate has always changed, and there is no such thing as a “natural steady state” climate, that does not entitle anyone to conclude that climate change since the start of the Industrial Revolution must, therefore, be the result solely of natural causes. Similarly, merely because there have been significant anthropogenic emissions of greenhouse gasses over the last 250 years is not, on its own, sufficient to enable anyone to conclude that recent changes in the Earth’s climate are, therefore, the result of human activity.
To answer the question of whether recent changes to the climate are primarily “natural” background changes that would have happened anyway, or the result of human interference, scientists have turned to modelling. Because the global climate is a vast, complex system climate scientists attempt to map the various dependent variables through computer-driven models called general circulation models (GCMs). A GCM simulates how the climate will change over time. A GCM cannot replicate the global climate system in its entirety; there are far too many variables. So climate modellers disaggregate the Earth system into small, constituent parts that can be easily analysed. These include, for example, changes in carbon sinks due to deforestation, increased radiative forcing due to greenhouse emissions, changes in albedo due to changes in land use, emissions from industrial agriculture, and so on. In order to assess the accuracy of a climate model scientists will evaluate how well it can simulate past temperature changes. The more accurate a model’s simulation of past climate change, the greater the degree of confidence that scientists will have in the model’s ability to predict future changes.
All climate models are arriving at very similar conclusions: first, temperature changes over the last two and a half centuries can only be explained if anthropogenic emissions are included and, second, the Earth’s climate will warm further this century, possibly catastrophically so. There are admittedly some uncertainties in climate modelling, for example, on the speed and scale of change and on the various tipping points in the Earth’s system, uncertainties that deniers have been quick to seize on as “evidence” that there is no scientific consensus on anthropogenic climate change. But only a very small minority of scientists disagree with the central thesis; that anthropogenic emissions of greenhouse gasses are driving recent climate change, and will continue to do so.
Why, therefore, is there so much debate, and claims from some that climate scientists are involved in a conspiracy? The answer is that there has been a widespread and well-funded denial campaign supported and/or funded by those who perceive that they will lose from tough measures to curb emissions. Prominent in this campaign are certain firms from the US oil industry, such as Exxon-Mobil, and certain politicians in the Republican Party. It is important here to distinguish between sceptics and deniers. A sceptic is a scientist who objectively seeks the truth but who has yet to be convinced that the available scientific evidence corresponds to the truth. Sceptics can play a useful role in questioning scientific evidence and identifying areas where future research is needed to eliminate uncertainty. Sceptics stand in contrast to deniers. Unlike a sceptic a denier does not seek the truth. A denier will ignore or undermine scientific evidence for political ends. Deniers argue that the science on climate change is unclear and unsettled, recent climate change could be entirely due to natural factors, the role of humans in causing climate change is unproven, and any social and environmental consequences of climate change are unlikely to be serious.
In 2006, ExxonMobil’s activities attracted the attention of the UK’s most eminent scientific institution. The Royal Society took the unusual step of writing to ExxonMobil to tell it that its statements on climate science are “very misleading”, leaving readers with “an inaccurate and misleading impression of the evidence on the causes of climate change that is documented in the scientific literature.” The Royal Society noted that some of the organisations that ExxonMobil has funded have engaged in “outright denial of the evidence that greenhouse gases are driving climate change” (Royal Society 2006). That same year two US Senators - the Republican Olympia Snowe and the Democract Jay Rockefeller - called upon ExxonMobil to stop funding climate change denial, saying that Exxon’s funding of an “echo chamber” of “non-peer reviewed pseudo science” had raised questions about the legitimate science of climate change (Snowe 2006).
Deniers have chosen to deny because they believe that doing so will enhance their own narrow interests, such as increasing public support for a certain political viewpoint or to maximise shareholder value for companies who profit from the exploitation of fossil fuels. The argument against them will be won only if they can be persuaded that funding denial and disputing science will materially harm their interests; for example, political parties find that engaging in organised climate denial costs them votes at the ballot box, and businesses find that denial loses customers. This is not the case at present. Denial of scientific evidence is a political strategy. Organised climate denial is only likely to cease when it attracts widespread moral opprobrium and harms the interests of the deniers. Whereas sceptics can be persuaded with new scientific findings, deniers cannot because for them the science is not the main concern.
By Vince Gauci, Lecturer in Earth Systems and Ecosystems science
Measurements. Without measurements there would be no evidence of climate change, nothing against which to gauge whether a change has occurred, natural or otherwise. We now have measurements in abundance spanning very long time scales. This is important because natural cycles of climate do occur (I guess the questioner means natural climate cycles when referring to 'weather cycles').
In relatively recent history measurements of temperature have been made directly with thermometers but deeper in time we need something that can take the place of a thermometer, something that can act as a record of temperature. Science has really come on in the last 30 years in this area and we now have a whole range of thermometer substitutes or 'climate proxies' that work in this way - they enable researchers to interpret the temperature at the time these features were formed. These proxies include isotopes of oxygen in ice cores, tree ring widths, ocean sediments etc. Many of these proxies of temperature are cross checked and so their measure of temperature becomes more robust and we have greater confidence in them as accurate records.
These records show that there are big natural changes over a range of time scales that are closely related to observable and predictable changes in Earth's orbit around the sun and are associated with the atmospheric content of greenhouses gases (as recorded in ice core bubbles). So climate change IS real.
The questioner though is probably wondering if human caused climate change is real. Recent measured increases in temperature can be placed against this historical context of natural cycles to see if the changes fit the trend. They don't. In fact they deviate markedly from these well established cycles. And this is where models come in. Climate models recreate Earth's climate in a computer from the ground up, incorporating ocean currents, many layers within the atmosphere, the composition of the atmosphere, even the spread and movement of vegetation and the change in the amount of light given off by the sun with time and reflected back out to space.
These models create numerical simulations of climate over time. To see how well they work you can compare them against measurements - recent and ancient. The results are rather good and recent climate warming can only be recreated in the models if the huge emissions of carbon dioxide and other greenhouse gases like methane from human activity are included in simulations. All this evidence tells us that human caused climate change is taking place. The evidence base is large, different research groups show similar results using different models - there really is a scientific consensus. To see the holes in the skeptic arguments for yourself go to www.realclimate.org.
Useful links
More about Professor Robert Spicer
With a first class BSc degree in Botany and a PhD in Geology, both from imperial College, London, Bob Spicer has always been interested in the evolution of life on Earth and its mutual interaction with climate. As a Lindemann Fellow and Research Fellow of the California Academy of Sciences he spent three years with the US Geological Survey at Menlo Park, California, where he began studying the vegetation and climate of the Arctic during the Cretaceous “greenhouse world”. On his return to the UK he was appointed to a lecturing post at Goldsmith’s College, London, before moving to Oxford where he was a University Lecturer in Earth Sciences, a Tutor at St Hugh’s College and Dean of St Hugh’s. During his time at Oxford he also spent three months as Guest Professor at the University of Vienna. In 1994 he took up a Chair and became Head of Earth Sciences at the Open University. Until recently he was Director of the Centre for Earth, Planetary Space and Astronomical Research (CEPSAR) at the OU. He has published over 100 journal articles and made numerous radio and TV appearances. He was a Co-PI on the public participation climate modelling initiative Climateprediction.net and has collaborated on modelling past and future warm climates. His current main research interest is the Lost World of the Cretaceous Arctic. This reconstructs the vegetation and climate near the North Pole during times of previous global warmth, and forms the blueprint for future management of the Arctic as a carbon sequestration system.
He said: “I study the evolution of high latitude vegetation and climate - this is primarily directed at times of extreme global warmth and focuses on the geologic records of Alaska, Russia, Australia, New Zealand and Antarctica. The research is directed towards providing ancient climate data with quantified uncertainties for testing numerical global climate models and has important implications for global change studies. The research also makes use of palaeo-data to model vegetation under possible future climates and to devise blueprints for biosphere management programmes and "designer ecosystems" for carbon sequestering ay high latitudes.”
More about David Humphreys, Senior Lecturer in Environmental Policy
More about Vince Gauci, Lecturer in Earth Systems and Ecosystems science
Dr Vincent Gauci is a in Earth Systems and Ecosystem Science and a member of the Department of Earth and Environmental Science Biogeochemistry group, which in turn is part of the cross departmental and cross faculty "Ecosystems Research Group (ERG). He is interested in the biogeochemistry of wetlands, with particularly interest in sulfur and nitrogen pollutant impacts on terrestrial/atmosphere exchange of chemically and radiatively important gases.
Vince researches the effects of acid rain sulfate deposition (both anthropogenic and volcanogenic) on methane emissions from both natural and artificial wetlands (rice paddies). He is also interested in the role of woody wetland plants in mediating trace gas emissions from wetlands. Vince has most recently worked as an academic consultant on the documentary ‘Hope in a Changing Cimate’ .
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