Climate Change: Your questions

Q: Is there any truth that temperature rose during the three day no fly policy after 9/11 and that vapour trails cause cooling?

A: Yes, in the day time at least. Because the skies were almost entirely free of contrails more energy from the sun was able to reach the earth’s surface, rather than being reflected back towards space by the contrails. This was used by some to argue that air travel actually helped to cool the planet through the reflection of sunlight by contrails. However, this overlooks what happened at night. With no contrails the infrared (heat) energy emitted from the earth’s surface is able to escape much more easily and so the surface is able to cool to a much greater degree. When there are contrails these act like strips of blanket – trapping the radiated heat and keeping the surface temperatures higher. So, when both day and night time temperatures are considered, contrails have a net warming effect on our planet, even before we consider the greenhouse gas emissions that they represent. An interesting recommendation made recently was to restrict night time air travel, and so confine the formation of contrails to the day time – where they have less of a positive climate-forcing effect. For more detailed information see this paper from the European Geophysical Union.


Q: Don’t you think that scientists involved in a particular area of research into climate change will like to play up the impact of their particular field (e.g. permafrost)? How can one person have an overview of the relative impacts of each contribution to global warming when they don’t have the expertise in all fields?

A: I don’t doubt there are some scientists who play-up the significance of their field in the context of global climate change. However, the Research Councils and other grant-awarding bodies use peer-review panels drawn from a range of disciplines to try and ensure that funding is given in a proportionate way – as far as the relativeimportance of one research field or finding, versus another. No, I don’t think one person can, in isolation, provide a fair appraisal of the whole subject. This is why the Intergovernmental Panel on Climate Change is so important, as it provides a peer reviewed synthesis of climate change science from around the world. Expert working groups are assigned to each of the key areas (Science, Mitigation and Adaptation), with each drawing together and assessing all of the published findings relating to climate change. Their assessments, published every 5 years or so, provide the best and most objective assessment available on climate change science and policy.

Q: Do you think it is possible to take control of ‘global warming’ or are we all doomed?

A: The problem is that we’ve already taken control of it through our emissions of greenhouse gases. As such we can alter just how much global warming we see by how much greenhouse gas we go on emitting in coming decades. I don’t believe we’re doomed, though we are already committed to some warming and some communities (e.g. those on low lying islands, Inuits) are already experiencing severe impacts.

Q: What is the single most effective thing that individuals can do?

A: For most, simply driving a smaller car would make a big difference.

Q: How do scientists outweigh the influence of politicians and oil companies?

A: I am not sure we do all that often. Our research can help inform politicians, and through them the oil companies, but as scientists we have no powers to set greenhouse gas limits for governments or oil companies. I suppose our greatest asset is the objectivity with which most climate change research is carried out and reported. However, we have had a consensus within the scientific community that human-induced climate change is real for more than a decade, yet political action has by and large failed to reflect this. Maybe the public trust scientists more than politicians – if so we have a key role to play in raising awareness.

Q: So what should we be doing about it? Individually, UK, EU, & global?

A: Individually: reduce our energy use at home, avoid air-travel wherever possible, give big-engined cars a miss, and opt for public transport, cycling and walking where we can.

UK: raise public awareness of climate change, provide better public transport, recycling facilities and incentives for energy saving in homes and microgeneration.

Set more stringent limits on emissions from business and industry, with an overall target of a 3% cut in UK greenhouse gas emission every year. Put more pressure on the US to re-enter negotiations on cutting emissions. Invest more heavily in renewable energy and development of renewable energy technologies.

EU: Set a EU-wide tax on air-travel to discourage the rapid growth in short-haul flights. Meet and exceed current EU targets for greenhouse gas emissions agreed under the Kyoto Protocol. Invest more in low carbon technologies, including Carbon Capture and Sequestration, with all new power stations being CCS-compliant. Ensure technology transfer to the developing world, allowing economic development in China and India to progress with the most efficient power-generation technologyavailable (e.g. clean coal power generation). Bolster the EU-wide carbon trading scheme, with independent assessment of point sources (power stations etc) and setting of annual emissions limits to achieve real year-on-year reductions.
Global: agree on a ‘son-of-Kyoto’ that brings in the developing-world countries and sets limits for greenhouse gas emissions for key economies such as China and India. Bring back on board the US and Australia, with ambitious greenhouse gas emission reduction targets and big penalties for non-compliance.

Q: If a square mile of trees is replaced by a square mile of grass, what is the difference in stored carbon?

A: A square mile of growing forest can be expected to lock away about 25 tonnes of carbon each year. In contrast, a square mile of farmed grassland would usually store about 1-4 tonnes of carbon per year. This is before you account for the carbon losses that result from deforestation and soil disturbance.

Q: How do you develop a consensus of opinion with conflicting evidence?

A: See comment on IPCC above. Their assessments provide an objective synthesis of the evidence, conflicting or otherwise.

Q: Is there a computer model (online) that the average person could put different sets of data into to explore different scenarios of climate change?

A: One good site is climateprediction.net where students can run their own climate model and at the same time contribute to a greater understanding of how global temperature will change during this century.

Q: What about volcanoes and sunspots?

A: Volcanoes and sunspots (an indicator of increased solar activity) are both important drivers of the earth’s climate. Up until the 20th century variations in these were pretty good at determining how the earth’s temperature changed. Since then they have been underestimating global temperature to a greater and greater degree, with rising anthropogenic greenhouse gas emissions being the widely-accepted culprit for the observed increases (human-induced global warming).

Q: A while ago a paper was published which showed a startling correlation between the length of the sunspot cycle and global temperature. Has this ever been accounted for?

A: Yes, works well up until the 20th century, but cannot explain more recent increases in global temperature. See the Intergovernmental Panel on Climate Change graphs showing natural and human-induced global warming.

Q: Is there any ‘good news’ from recent research on global warming / climate change or is everything worse than predicted previously?

A: Carbon Capture and Sequestration (CCS) technology is looking much more of a possibility. Recent pilot projects have shown that capturing the CO2 and putting it back underground in old oil and gas wells can be done on a large scale and indicate that the CO2 will remain stable and locked away from the atmosphere for more than 5,000 years.

Q: How far away are we from the point of no return? The ultimate tipping point?

A: Your guess is as good as mine. We’re already committed to some warming, at least 1-2 degrees this century would be my best estimate. Given the lag time inherent in global warming caused by the massive heat-store that is the oceans, it is unlikely our climate will return to what it was for our grandparents for at least 50,000 years. Some models suggest that tipping points such as drying of the Amazon will be passed within the next few decades but, as ever, there are substantial uncertainties. The only certainty we have is that the tipping points are there and we are moving closer toward them.

Q: Is enough being done to inform the public about this huge catastrophe?

A: No, I don’t think so. Things are improving and awareness is increasing. But too often raised awareness comes in the form of “we’re all doomed!” rather than laying out the facts and showing that we actually have a choice in all this.

Q: Does the fact that tropical plants use carbon for photosynthesis have any mitigating effect on CO2/O2 balance?

A: Yes, in fact they are vital for keeping a lid on things. Of the 6 billion tonnes of carbon we kick out into the atmosphere each year from burning fossil fuels, only about half stays in the atmosphere and contributes to enhanced global warming. The rest is taken up and stored by the land the oceans through primary production via photosynthesis.

Q: Developing countries are becoming massively industrial. Could they produce so many atmospheric pollutants (how regulated are emissions?) that ‘global dimming’ may reduce the extent of global warming?

A: We’re already seeing the effects of this, the skies are clearing above North America and Europe while they are dimming over large areas of Asia. However, the particles that cause global dimming usually only last weeks or months in the atmosphere, while greenhouse gases hang about warming the planet for years, decades or centuries (methane = 12 years, carbon dioxide = 100 years, nitrous oxide = 120 years).

Q: Why are the government / oil companies not putting more money into bioethanol / non-fossil fuelled transport systems?

A: They are starting to. BP and British Sugar have just announced a large-scale scheme to produce biodiesel and the government is aiming for a big rise in the percentage of biofuels used by transport: 5% by 2010. However, there is a limit to what is possible via biofuels without growing food specifically for their production. My own view is that they should be confined to the use of waste (straw, paper waste, forest residues) rather than relying on the growth of extra crops that could feed people rather than cars.

Q: What impact has any of the changes we have made over the last 20 years had on temperature change? Have temperatures gone down as people have tried to implement them?

A: Greenhouse gas emissions have continued to rise rapidly, and so have global temperatures. Compared to a business as usual scenario, greenhouse gas emissions have been cut by some nations, but as yet the impact of this reduction is too small to have made a significant difference to global temperature.

Q: What can a school student do to lower CO2 levels?

A: Use the school bus, walk or cycle. Be the scourge of energy waste at home – stop standby power wastage, turn of lights etc. when they’re not being used, recycle, holiday in the UK, lobby their MP, their council, their parents and their head teacher to cut emissions. Grow some of their own food in their garden or at school, pull on a jumper rather than ramp up the thermostat. Become a Climate Change Champion see the Department of Environment, Food and Rural Affairs for details of the current Champions.

Q: What is the effect of volcanic eruptions on global CO2 levels?

A: Very minor. Volcanic eruptions can be big ‘point sources’ but to put their total CO2 emissions into perspective (from US Geological Survey. Volcanoes emit between about 130-230 million tonnes of CO2 into the atmosphere every year. This estimate includes both subaerial and submarine volcanoes, about in equal amounts. Emissions of CO2 by human activities, including fossil fuel burning, cement production, and gas flaring, amount to about 22 billion tonnes per year Human activities therefore release more than 150 times the amount of CO2 emitted by volcanoes.

Q: At what point does global warming become irreversible?

A: We are already committed to a certain amount of warming, so in that sense it is already irreversible. In the longer term (millennia) one might expect human-induced warming to once again become secondary to natural drivers of climate (e.g. solar activity) and so the earth’s temperature may decrease once more.

Q: Is it probable that humankind as species will adapt to the gradual global warming/cooling? I wonder if it is true when they frighten us with a theory of human species dying out as dinosaurs.

A: Yes, we will adapt to some extent, though the resources for adaptation in the developing world are generally very limited. Climate change is very unlikely to put an end to the human species. What it will certainly do is threaten some of the most vulnerable human communities: the Tuvalu islanders and the Inuit for example. At the higher end of the predicted global temperature rises this century (4-6 degrees centigrade), civilisation itself may be threatened. A combination of widespread drought, famine and disease, could lead to mass migration, political unrest and war. Throw in destruction of some of the world’s largest cities due to sea level rise and collapse of the global economy and we have a truly nightmarish scenario by the end of the century.

Q: Who are we to believe? Some scientists say that global warming or cooling is a natural phenomenon, which can’t be influenced. Some say that the quickly approaching global warming will lead to Armageddon… Who are we to believe?

A: Neither of these fits with the current scientific consensus. Natural phenomena (volcanoes and solar activity) can’t explain the warming we’ve seen since 1850, increasing greenhouse gas concentrations remain the only likely explanation. My suggestion would always be to read the information provided by the Intergovernmental Panel on Climate Change (IPCC) if you want to separate fact from fiction. The IPCC represents a synthesis of thousands of independent climate change scientists around the world.

Q: I heard that the axis of the equator is deflected by 13 degrees. Does it influence the global climate?

A: Yes, variations in the tilt of the earth, our position in our orbit around the sun and the sun’s activity all affect our global climate. Any analysis of global warming trends must take these factors into account.

Q: Steam influences the climate change greatly. This gas is mainly responsible for global warming. According to the latest data, the ocean space has increased, hence the increase of water steam. Why do some scientists think we should expect the global cooling when in fact the amount of greenhouse gas (which largely consists of steam) gets bigger?

A: Yes, water vapour is the most important of the greenhouse gases, with CO2 being the most important man-made greenhouse gas. The effect of increasing amounts of water vapour in our atmosphere due to global warming is still an area of much disagreement. Though water vapour in the upper atmosphere leads to more global warming, more cloud formation at low levels reflects more of the sun’s energy back into space and so leads to a cooling effect. At the moment we think that the combined effect will be a slight warming due to increased water vapour, but the uncertainties around this remain large.

Q: Which city/country on the planet will be the most desirable for living in after the global warming/cooling has happened?

A: Firstly, nowhere less than about 10m above sea level. Then, nowhere where the water supply depends on glacial melt water or is already stretched due to low summer rainfall. Then, nowhere within the expansion zone for malaria given a 6 °C rise in global temperature. Then take out anywhere already prone to hurricanes, ice storms, land slides, flash flooding and droughts. As we can’t rely on the global economy having survived intact, the place also would have to be essentially self-sufficient in food and water. Finally, if it is so free of all the negative impacts of global climate change then it would have to be able to cope with a huge influx of climate change refugees. What place is this? I don’t think it exists.

Q: What awaits us finally, global warming or new ice age? The film “The Day after Tomorrow” by Roland Emmerich: is it fiction or a scientific probability?

A: I don’t think there is a ‘final destination for our climate’ for humankind – over the next 1,000 years we can expect global warming to predominate and sea levels to rise by many metres. In the longer term the climate will continue to be affected by both humans and by natural factors such as solar and volcanic activity. The strange weather in the Urals can’t be directly attributed to climate change, only over a sustained period can we say whether such odd weather is due to a real change in climate caused by global warming, rather than natural variations. The Day after Tomorrow scenario has a very, very low probability over the next few centuries, but is possible on the scale of millennia. The shut-down of the Atlantic conveyor which brings warmth to us from the equator would require a huge amount of freshwater input from the Greenland ice sheet and elsewhere. Though there is evidence this has happened in the past, at the moment there may not be enough water locked up in the ice cap and glaciers to cause such a shutdown.

Q: Do you think what we are having now is global warming or cooling? Or perhaps nothing global is taking place at all?

A: Without a doubt, global warming is happening. We’ve seen a 0.6 °C increase in the last century, with the rate of warming increasing markedly in the last 20 years. Global is the key here – if you take one region or another you can argue both for very rapid warming or, in a few cases like the dry valleys of Antarctica – some slight cooling. Only by looking at the global temperature can we cut through these regional variations and get the real picture.

Q: What do you think are the main problems of digital climate modelling? E.g. theory inadequacies, shortage of global or operatic data, insufficient calculating techniques, drawbacks in coordination or financing?

A: Lack of computing power is a big one. We need thousands of runs of the global climate models to reduce their uncertainty, but this eats up an awful lot of resources. Then there are the scientific uncertainties such as the impact of increased water vapour. The climate modelling community are making great strides in reducing these uncertainties, but at the moment we are still left with a range of global warming of between 1.4 and 5.8 °C this century – a big range!

Q: What can you say about natural disasters happening lately?

A: Any single natural disaster is almost impossible to attribute directly to man-made climate change. There have always been such events, but with a changing climate we are likely to see an increase in their intensity and their frequency. Only over time can we identify real changes in climate leading to increased natural disasters. Sea level rise will become the benchmark this century, with thermal expansion and increased ice melt leading to up to 80cm of sea level rise and so being directly responsible for ‘natural’ disasters in low-lying areas such as Bangladesh.

Q: A new report from UNEP (on changing climates, role of sustainable energy resources, carbon emissions) points at the connection of problems of climate change and sources of sustainable energy. The report tells about the forming consensus among scientists and politicians on the fact that the absolute threshold of global warming (which is 2 °C above the pre-industrial level) can prevent the most threatening aspects of climate change. Will the consensus be ever reached?

A: This is indeed the level at which the most dangerous impacts of climate change may start kicking in. It is at this temperature that the many positive feedbacks to global warming – such as drying of the Amazon and melting of methane-rich permafrosts – are thought to become important. The consensus is pretty strong already – what we need is a definitive level of CO2 in the atmosphere that we must stay below to avoid warming of more than 2°C. The current thinking is that this is about 500-550ppm, but under a ‘business as usual’ emissions scenario we may greatly exceed this level.

Q: Many people say climate change will lead to tragic consequences, but it is quite possible that is the way nature is healing itself to save the living world, like a lizard throwing off its tail to save its life. So perhaps it is the same process, to save the planet the humankind should go as the main destructive force?

A: Yes, this Gaia hypothesis first introduced by James Lovelock is very thought provoking. Certainly the climate change we are causing threatens many communities and may threaten civilisation itself. It’s doubtful though, whether climate change will mean human beings will disappear completely.

Q: Perhaps it is too early to make such global conclusions on greenhouse gas effect on the basis of a relatively short period of weather observation. Can we say that the climate regulates itself and that humankind influences the climate in the same way it did 200 years ago?

A: Unfortunately no. As we’ve increased our emissions of greenhouse gases over the last 200 years the world’s forests and oceans have regulated some of this – taking up about half of that emitted. But the rest has remained in the atmosphere and concentrations continue to increase. They are now much higher than at any time in the last 800,000 years. This increase has led to a rise in global temperatures above anything that could be explained by natural drivers of earth’s climate.

Q: What about the ozone hole?

A: The ozone hole, as it is known, should be reducing in size as concentrations of the main ozone-destroying chemicals (mainly CFCs) fall. However, global warming has an indirect effect here in that it causes the warming of the lower atmosphere (the troposphere) but cools the stratosphere (above about 15km). The colder it gets in the stratosphere the better the reaction that destroys ozone progresses. So global warming is in effect helping to prolong ozone depletion.

Q: The media told us recently that the average yearly temperature will decrease during the next 50 years due to a decrease of sun activity. What do you think?

A: If it were only the sun’s activity that determined global temperatures then this may be the case. However, greenhouse gases also play a leading role in determining global temperatures and, as these are set to increase, so will global temperatures.

Q: How did the climate change in the last 10 years? What are the next changes?

A: The 1990s were the warmest decade (so far) since records began (in 1861), 1998 was the warmest year on record, 2005 was the second warmest ever globally and the warmest ever in the northern hemisphere. 2006 was the warmest year on record in the UK and 2007 is predicted to break all the global temperature records yet again.