"It's 460 degrees Celsius on Planet Venus"

Alternativtext As the economic crisis continues and governments spend billions of Euros on rescuing their choking car industries, we shouldn't forget about the much more severe climate crisis, warns climate expert Jean-Louis Fellous from the European Space Agency. If key decisions are not taken now, it could be too late to stop irreversible global warming.

sg: Mr. Fellous, you have been director of several satellite programs for the French Space Agency (CNES) and you are currently working with the European Space Agency (ESA). How can you study the climate from space?

Jean-Louis Fellous: We can measure a number of environmental parameters with our satellites. The first artificial satellite was launched in 1957, the first meteorological satellite in 1960. Of course it was still very simple, it just took pictures of the clouds. Nowadays we have dozens of satellites flying with a wide variety of instruments capable of measuring something like 30 different parameters of interest, regarding the atmosphere, oceans or land. For example, the vertical temperature profile – at different heights – wind fields, clouds, aerosols – those small particles which are in the atmosphere. We can also measure the radiation going up and down in the atmosphere.

sg: How can you measure the vertical temperature profile with mere images?

JLF: This is very complicated. Actually satellites do not only take pictures! They make measurements. For example you can measure various emission lines from different altitudes in the atmosphere. Using a complex mathematical inversion system you can come back from this “visual” spectrum profile to the temperature. Equally this applies to other parameters like humidity, concentration of atmospheric gases like ozone and so forth.

sg: That relates to the atmosphere, but can you even look deep inside the oceans too?

JLF: Only indirectly, as electromagnetic waves do not penetrate deep into water. What we do is measure the sea surface temperature, and we look at the sea surface topography which gives us information about the currents inside the ocean. We also can measure the surface reflectance which gives us information on the content of biological pigments on the surface of the ocean, we can draw maps of surface winds and waves, monitor the sea ice and also the ice masses over the continent. We take pictures of land surfaces, which serve evaluating the vegetation cover, the lakes extent and surface temperature, we can measure the biomass content. All those wide variety of techniques help us evaluate the climate and detect climate change.

sg: How long has climate change actually been studied?

JLF: It is only very recently that scientists became aware of climate change and that climate change became an issue of scientific research. When I was a student of meteorology in the 1960s we talked about “climatology” as a rather boring discipline. It was simply about measuring the same parameters over a long period of time, defining “climates” as the sum of weather observation for thirty years over large areas. Scientists generally believed that the climate was stable. This did not change until the 1970s.

sg: How did it come to this?

JLF: Very important for the discovery of Climate Change was an international expedition to the Antarctica of the third International Polar Year . Scientists from different countries tried – while exploring also other geophysical matters – to understand better how the earth atmosphere-ocean system works. Therefore they collected data of all kinds. One US scientist, Charles Keeling, started measuring the concentration of carbon dioxide in the atmosphere on top of the Mauna Loa volcano in Hawaii , This location in the Pacific Ocean is far away from big cities or industrial centers and their pollution, thus the atmosphere there can be considered as homogeneous as possible. When Keeling started his measurements the carbon dioxide concentration in the atmosphere was of about 315 ppm ( parts per million , i.e. cm3 per m3), at this moment it has reached 385 to 390 ppm.
But it wasn't until the mid-1970s that the increase of carbon dioxide in the atmosphere was related with the increase in temperature: what we today call the (additional) greenhouse effect.

sg: Could you explain what the greenhouse effect is?

JLF: Essentially, the earth receives energy from the Sun in the form of light. 70 percent of this energy enters the system, while 30 percent is reflected by the clouds, ice and other clear surfaces.
Certain gases, including carbon dioxide (CO2) and methane (CH4), are transparent to most of the light arriving from the Sun but are quite opaque to infrared radiation. These gases are called greenhouse gases. What happens is that the incident solar energy passes through the Earth's atmosphere and is converted into heat by absorption at the surface. In turn heated Earth surfaces radiate upward, but this infrared radiation does not easily flow into space: a significant fraction remains trapped in the atmosphere (which is warmed from below, and not from the top) due to its being absorbed by greenhouse gases. As more such gases are released in the atmosphere, as the industry, forest fires, cars and so on emit more gases, this effect is amplified. It is like if you were in your bed and you cover yourself with an additional blanket. You will feel warmer very soon: As the opacity of the atmosphere to infrared radiation is increased, it is getting warmer.

Aerosols over India

sg: When was this model first understood?

JLF: Actually the greenhouse effect has been known since the 19th century. A French scientist, Joseph Fourier, described in the 1830s for the first time, that gases in the atmosphere would effect the temperature on Earth. He was chiefly interested in the possibility that a lower level of carbon dioxide gas might explain the ice ages long time ago. But at the end of the century a Swedish scientist, Svante Arrhenius, who was strongly influenced by Fourier, predicted, that the Earth's climate could warm up, as we were putting always more industrial emissions in the air . In any case, Arrhenius and others were not taken seriously. Though the physical knowledge was there, there was no immediate effort undertaken to develop a theory and to predict possible changes using measurements and so forth. Only in the late 1970s did a few scientists draw attention to the fact that a major phenomenon might be taking place, one which we were ignoring. When I was a student, the best individuals would rather study fundamental physics than waste their time with something like meteorology and climate which was still not conceded any importance. Today of course understanding the climate system is considered to be one of the most complex and important issues.

sg: What did scientists do to understand the climate better?

JLF: The most important initiative – though of course there were some international research programs – was set up by the UN World Meteorological Organization . The IPCC, the Intergovernmental Panel on Climate Change , built on the results gathered by international programs in the 1980s and 1990s, which led us to understand better how the tropical region influences the global atmosphere, for example the famous El Niño phenomenon.
Another important element was that scientists now understand that the weather is basically influenced by short-term interactions of the atmosphere, while the climate's long term changes are mostly influenced by the ocean, as the slow part of the system. The oceanic systems evolve over centuries, while the atmosphere changes within weeks, days or even hours. So if you look at the climate, it is very important to look at the oceans, their circulations and currents and so on. The World Climate Research Program put considerable emphasis on understanding the global ocean circulation and its role in climate and climate change.

sg: How did you get involved with this research?

JLF: When I joined CNES, the French Space Agency, in 1982, I got involved into those issues as the manager of the first satellite program to monitor the ocean circulation. If you want to measure ocean currents and so on, you can imagine that it is extremely difficult to do this from a boat as you are on the sea's surface. After launching the satellite in 1992, within a week, we had better data than those collected in all the previous centuries. It was a real revolution for scientific research.

sg: A revolution of understanding that humans could be responsible for climate change?

JLF: Yes, the first report of the IPCC in 1990 stated that there was the possibility of human induced climate change. The second report in 1995 was already stronger, that there was human responsibility for earth's warming. The 2001 report mentioned a likely (66%) and discernible influence of human activity on the planet's climate. The 4th IPCC report published in 2007, the most recent one (the next will probably be published within a five years time), states that the probability that industrial and other human made emissions are responsible for the climate change is very likely (over 90%).

sg: What do you think, how and why climate change became a mainstream political issue?

JLF: The public and political reception of that phenomenon was surely influenced by several disconcerting events which occurred in the past few years (though their relationship to climate change cannot be asserted). Climate change can be seen as a slow evolution. But it is not only about the slow trends, like the rising of sea level or melting down of the glaciers. It also is about the single, big and not seldom disastrous events of climate change. You remember for instance the big storms Lothar and Martin in Central Europe in 1999. Nothing like this had happened for more than 500 years, buildings which had survived all those centuries were suddenly destroyed. There was no precedent whatsoever. In 2003 we had this heat-wave costing over twenty thousand lives and doing great damage to the ecological system. Only two years later Hurricane Katrina destroyed almost the whole city of New Orleans. Those kinds of weather extremes were barely observed before.

sg: But are those events really related to the climate change?

JLF: Well, we do not (and will never) have the ultimate proof of that, though it is very much likely. There are many good reasons to believe that climate change goes hand in hand with increasing anomalies in weather.

sg: Was it only these extreme weather situations which aroused public attention?

JLF: On a completely different front the Stern review was also very important of course. Sir Nicholas Stern as an adviser to the UK government stated, that the cost of actions aimed at limiting the rise of temperature to two degrees Celsius represented 1% of the Gross Domestic Product of all countries, while the cost of inaction would be at least 5%. It was an argument which appealed to the natural instinct of politicians. At the same time Al Gore's documentary naturally did a very important job for the increasing awareness of the public. And also the fact that he and the IPCC were awarded the Nobel Peace Prize for their work.

sg: And now with the economic crisis all that danger is forgotten and we spend billions of dollars on rescuing our car industries?

JLF: Politicians usually do not think in the long term. They are short-sighted, as the electoral terms are usually some four or five years. At the moment every European politician is afraid that the car industry might collapse and unemployment will rise significantly. This is not wholly true for Obama, who decided to use this unique opportunity to force the automobile industry in the US to build more efficient and also electric cars. Anyway, focusing on this short-term crisis instead of the climate crisis which will last for centuries would undoubtedly be disastrous. I think the biggest problem is that, whatever what we do now, we will not see the results ourselves. Measures taken now would show their effects not before the end of the century. That's a huge political problem, because you have to convince people to do something now, not for themselves, but for future generations.

sg: Why would it take such a long time to stop the warming up?

JLF: Climate change is already very far advanced. Carbon dioxide continues to pile up in the atmosphere at an ever-increasing rate. But also the oceans store a huge reservoir of energy which is still to warm up the climate. If you observe the oceans from space, they seem almost black. That means that they reflect almost no solar light. They absorb 95% of the energy which reaches the ocean surface. This absorbed energy is inside the oceans, transported by currents and will come up to the surface at some point. Even if we were to stop all CO2 emissions from now on, the warming which is kept within the ocean is still there, and will produce future effects.

sg: If we do not take those decisions, some scientists say there could be a point of no return.

JLF: Yes, some even say if we do not do anything now, within the next three years, it will be too late for anything to stop catastrophic warming happening. Anyway, if we look at the results of some different models for future climate scenarios, at least some things are pretty clear. If we take the worst case scenario from the IPCC report from 2001, we can see that the actual CO2 emissions exceed the most pessimistic views, so that the real development of the climate until now, in 2009, is even worse. The worst case IPCC scenario still proved to be overly optimistic. What we must be really afraid of is the possibility that system falls into a trap, and reaches a point of no return from where it never could go back to its former state. Think, for example, of an accelerated melting of polar caps.

sg: Is there any limit to the possible temperature increase?

JLF: Venus is a planet with a temperature of over 460 degrees Celsius, because there is an enormous greenhouse effect. The atmosphere basically consists of carbon dioxide. All the rest has been blown out to space. Nobody knows what will happen if we pass a certain limit of temperature increase.

sg: This does not sound too reassuring. Do you still have hope anyway?

JLF: Yes , I do. But we need a strong vision and a great deal of leadership. The technology is already there. We do not need some miraculous inventions, as some people are preaching. The average car, of the billions of cars we drive on Earth, consumes say 8 liters per 100 kilometers. For a long time, we have been able to build cars which only use 4 or less. Two US economists have shown that only 15 different measures like this one, based on existing technology, could meet the world's energy needs over the next 50 years and at the same time could limit atmospheric CO2 to a trajectory that avoids a doubling of the pre-industrial concentration. It is just a matter of decisions.

sg: What are your expectations as regards the climate conference in Copenhagen this December?

JLF: Compared to the previous situation with the Kyoto Protocol , there are a number of new elements: the reversal in the US attitude, the strong European pressure in favor of stringent commitments to reducing greenhouse gas (GHG) emissions, the new voice of emerging economies (China, India, Brazil), the understanding that most advanced countries will have to help financially the less developed countries, etc. My hope is that significant commitments to reducing CO2 and other GHG emissions will be agreed upon with reference to 1990, that serious technology transfer efforts will be accepted by the most advanced nations to help less developed countries to reduce poverty while avoiding excessive use of fossil fuels, and that verification tools (which notably require Earth observation by remote sensing) will be used to enforce the commitments. This is particularly important because multilateral environmental agreements without verification measures are simply hollow.

Jean-Louis Fellous

Alternativtext worked as an atmospheric scientist before joining the French Space Agency, CNES, in 1982 as Program Manager for the US–French Topex/Poseidon oceanography satellite. He headed the Earth Observation Programs at CNES from 1998 to 2001, and was director for Ocean Research at Ifremer, the French ocean research institute, from 2001 to 2005. He currently works with the European Space Agency as coordinator of Earth observation satellite programs related to climate, environment, and security. He is the Executive Officer of the Committee on Earth Observation Satellites (CEOS) and a co-president of the Joint Technical Commission on Oceanography and Marine Meteorology (JCOMM). Fellous is author and co-author of several books, published in French, on climate and environmental issues such as “Avis de Tempête – La nouvelle donne climatique” (Tempest Warning – The New Climatic Order)c, “Comprendre le changement climatique” (Understanding Climate Change) and “Eau, pétrole, climat : un monde en panne sèche” (Water, oil, climate: a world running on empty?”), as well as one title in English “Facing Climate Change Together” (Cambridge University Press).

Arrhenius' greenhouse law

If the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression.

This simplified expression is still used today:

ΔF = α ln(C/C02)

Atmosphere temperature

"The temperature of the atmosphere varies with the distance from the equator (latitude) and height above the surface (altitude). It also changes over time, varying from season to season, from day to night and irregularly due to passing weather systems. If these variations are averaged out on a global basis, a pattern of average temperatures emerges for the atmosphere. The vertical temperature profile (the way temperature changes with height) divides the atmosphere into four layers: the troposphere, the stratosphere, the mesosphere, and the thermosphere."

(cited from: Atmospheric Temperature - The Vertical Temperature Profile, The Sun's Role In Atmospheric Temperature, The Greenhouse Effect )

Vertical temperature

"Averaging atmospheric temperatures over all latitudes and across an entire year gives us the average vertical temperature profile. This plot is sometimes called a standard atmosphere. The average vertical temperature profile suggests four distinct layers. In the first layer, called the troposphere, average atmospheric temperature drops steadily from its value at the surface, about 290K (63°F; 17°C) until it reaches of minimum of around 220K (−64°F; −53°C) at a level about 6.2 mi (10 km) high. This level, known as the tropopause, is just above the cruising altitude of large commercial jet aircraft. The drop of temperature with height, called the lapse rate, is nearly steady throughout the troposphere at 43.7°F (6.5°C) per 0.6 mi (1 km). At the tropopause, the lapse rate abruptly shrinks to very low values. Atmospheric temperature is roughly constant over the next 12 mi (20 km), then begins to rise with increasing altitude up to about 31 mi (50 km). This region of increasing temperatures is the stratosphere. At the top of the layer, called the stratopause, temperatures are nearly as warm as the surface values. Between about 31–50 mi (50–80 km) lies the mesosphere, where atmospheric temperature resumes its drop with altitude and reaches a very cold minimum of 180K (−136°F; −93°C) at the top of the layer (the mesopause), around 50 mi (80 km). Above the mesopause is the thermosphere, which as its name implies is a zone of high gas temperatures. In the very high thermosphere (about 311 mi (500 km) above Earth's surface) gas temperatures can reach from 500–2,000K (441–3,141°F; 227–1,727°C), depending on how active the sun is. However, these figures are somewhat misleading. Temperature is a measure of the energy of the gas molecules' motion. Although they have high energies, the molecules in the thermosphere are present in very low numbers, less than one millionth of the amount present on average at Earth's surface. If a person were in the thermosphere, it would feel to them much more like the icy cold of space because such a small number of energetic gas molecules would be unable to transfer much of their heat energy."

(Cited from: Atmospheric Temperature - The Vertical Temperature Profile )

Bildquellen in Reihenfolge: NOAA (public domain), Damien Fellous/Libre arbitre, NASA (public domain)


Themen: Klimawandel
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