Lennart Bengtsson sent me this manuscript and asked for publication. Maybe a few words about who Lennart Bengtsson is are in order. He is a trained meteorologist, was head-of-research and later director of the ECMWF, the European Center for Medium Weather Forecast. Later he became one of the three directors ol the Max Planck Institute of Meteorology in Hamburg, where he was responsible for the development of the global atmospheric model ECHAM (and other scientific issues). After retirement he is active in Bern as Director Earth Sciences at the International Space Science Institute and professor at the Environmental Systems Science Center at the University of Reading.
Lennart Bengtsson: Global climate change and its relevance for a global energy policy
The first in-depth discussion of the Earth’s climate and it possible change due to increasing greenhouse gases in the atmosphere started more than half a century ago but was restricted to a small numbers of leading atmospheric scientists. Since then the situation has changed beyond recognition. Over the last two decades climate change has evolved into a key worldwide issue with major involvement of media,the political community at different levels and the public at large not the least on Internet. The views vary widely but the dominant opinion is that climate change is genuine and a potential challenge to the world community at least in the longer perspective. This is also an opinion shared by a majority of leading scientists in the field. At the same time there is an increasing tendency towards a polarization in the opinion on climate change with on one hand a preference for dramatic and extreme consequences such as so called tipping points and on the other hand a tendency to even question basic aspects of the physics of climate change.
The relation between temperature and greenhouse gases in its very simplistic form has been known since the second half of the 19th century. The effect of the greenhouse gases can be seen as a warm overcoat preventing the surface in radiating away the heat to space. However, the warming is a complex process incorporating the dynamics of atmospheric and ocean flows and interactions of the many components of what is now called the Earth’s system. This includes in addition to the atmosphere, the oceans, the land surfaces and the land ices. Its study requires advanced computer models and other tools for its analysis and understanding. It also requires accurate observations for validation and monitoring as well as special measurements for the development of many crucial aspects of the models. It is in fact an immensely complex undertaking that is virtually impossible to explain to the public in a readily understandable way. This has lead to a tendency towards oversimplification that has contributed more to confusion than to a thorough understanding. However, because of the strong public interest we are now facing a dilemma as the public and the political community have become too much involved in the climate change debate influencing the actual science and this not necessarily in a positive way as it implies an arbitrary selection of priorities and preferential issues.
Natural processes drive climate and practically all kinds of extreme weather have always been part of the climate and are practically unrelated to the modest warming we so far have had. The effect of increasing greenhouse gases is a slow but relentless process that will have to be dealt with but will require more time and better insight in key processes.Some events are seen as very dramatic as the reduced Arctic summer ice, others, even more puzzling, such as the surprising lack of warming in the tropical troposphere is hardly discussed.
The problem is that the global warming is mainly caused by the emission of carbon dioxide and thus directly related to energy production by fossil fuels that has dominated and still dominates the energy production by more than 80%. To significantly reduce or eliminate fossil fuel is not feasible on a time-scale shorter than several decades, as it requires fundamental technical breakthrough in energy generation or alternatively a major change in our life stile. As the second alternative is hardly possible to achieve in a world with mostly open societies, it is obvious that the world community is facing a gigantic challenge. Additionally many parts of the world are suffering because of a lack of suitable energy and the need is further underpinned by the fact that the world’s population will increase by another two billion humans in the next three decades.
Some comments on the present situationSince the end of the 19th century the global warming amounts to about ¾ °C. This is a very modest increase in view of the fact that the greenhouse effect has increased by almost 80% or with about 3W/m2 as can be seen from Figure 1 below. If we translate this to an equivalent CO2-effect it corresponds to an increase from 280 ppm to ca. 490 ppm.
Figure 1. Correlation between the global temperature and the radiative forcing of the well-mixed greenhouse gases 1850-2012. The relation between the vertical and horizontal scale is 0.314°C/Wm2. (After S Schwartz). During this time the equivalent CO2 effect has increased from 280ppm to 490 ppm.
The global temperature has not increased steadily but in irregular intervals. Typical features are a distinct warming trend 1910-1940, a slight cooling trend 1945-1970 followed by the sharp warming trend until the end of the 20th century and finally the last 15 years without any clear warming trend. The lack of any significant warming in the tropical troposphere since the beginning of space observations in 1979 is particularly intriguing in particular as present models show a warming trend over the same time of 0.3-0.4°C in the average, figure 2. Such results, scientifically very puzzling as they are, have hardly received any media attention but instead the public has been overwhelmed in recent years by excessive reports of a rapid and threatening global warming very soon running out of control, unless the most drastic steps are taken to stop it. If there are no obvious global signals available, suitable arguments are created from an endless number of extreme weather events. The fact that similar extreme weather has been found to be a property of the present or undisturbed climate is not recognized. The global warming has been taken out of the hands of the meteorologists and traditional climatologists and is now run by professional media experts and different well-recognized members (political or otherwise) of the general public that have found the present climate hype to be a suitable way to remain or be obtain a place in the media limelight.
For some parts of the industry as well as for different NGOs such as Greenpeace and WWF a threatening climate warming have become a necessity and a source of extra income as it provides continued subventions for wind and solar energy as well as contributions from worried parents and grandparents that are anxious to protect their children and grandchildren from an approaching climate catastrophe.
In the very emotional climate debate today is it hardly possible to have a sensible and balanced exchange of views. If you do not support climate catastrophes as the one recently from the World bank, you are placed into a deniers box and accused to support the interest of the oil industry or alternatively that you are a man in a senior age and therefore unable to understand the concerns of the younger generations. Some of our colleagues are exposed to a powerful group pressure or that of a politically correct boss. The real genuine interest in climate and climate processes is fading away as the interest is confined to the concept of climate typical of the general public or rather I shall say the predominant or politically correct concept of climate.
Among meteorologists and well educated people the role of the greenhouse gases in the atmosphere is relatively well understood such that an increased concentration leads to higher temperatures at the surface and a cooling of the lower stratosphere. This has also been observed. The problem is not the direct effect of the greenhouse gases that is relatively minor, with about 1° warming for each doubling of the CO2 concentration, but the feedback processes in the climate system. Some of these are likely to be positive such as water vapour; others such as clouds are still not well understood. The feedbacks of the climate system dominate the outcome but are unfortunately so far not well handled by models. It is the main cause to the large differences between models.
However, the really important question is to know how much warmer it will be and how fast this is likely to happen as this determines a realistic and sensible cause of action. In spite of all research and modelling experimentation we are actually less sure what will happen than what might appear from all reassuring reports that dominates the media. Irrespective of all worrisome media report on the drama of climate change, climate is in fact warming much slower than anticipated. The very first climate simulations that were made almost a quarter of a century ago and at least according to the simulation by the MPI model in Hamburg, the global warming today should rather be 1.25°C than the present 0.75°C. And this is spite of a relatively large (cooling) aerosol effect of the Hamburg model that at the time was larger than the present view of IPCC today. The tropics are a crucial area as it is here where the greenhouse effect is largest. During the period 1979-2012 for which we have reliable observations, the warming of the lower tropical troposphere, 20°S – 20°N, has only got about a third of the warming compared to what is predicted by present climate models.
Figure 2. Tropical temperature changes at different pressure levels for 1979-2012 and for different observing systems and for a range of model experiments used in IPCC AR5 (courtesy J. Christy) The warming trend my the models is about 3 times larger than the observations.
There is no simple explanation to this, except that the planet is capable to get rid of the heat more effectively than in the models. This can be due to errors in handling the clouds or that the water vapour effect is overestimated and that in reality the atmosphere is loosing heat to space in regions of very dry air that is not well represented in models. Alternatively more heat is effectively transported into the depth of the oceans. However, the observational records are clear and the global warming is proceeding much slower than generally is anticipated.
There is a need to rethinkInstead of being grateful for this comforting result the reaction is rather the opposite. In the almost hysterical climate hype of today a less dramatic warming is not very well received as all political correct members of the public would prefer to hide this uncomfortable fact by following the popular maxim of letting the ends justify the means. From the standpoint of the green movement all political efforts, even extreme ones, are required as they wish to abandon fossil energy as well as nuclear energy and this at a time when the world population is increasing and where the lack of suitable energy is a primary obstacle towards a better life. To achieve this in a short period of time is like the squaring of the cube. Even Germany with its considerable economical and technical resources has been forced to build a number of fossil fuel power stations (using lignite) to replace nuclear power stations, as this is the only way to assure a steady supply of electricity in a time scale of a few decades. Renewable energy can only serve as complements as there is presently no way to store electricity effectively in the amounts required.
The global climate policy has unfortunately been a failure mainly because of an inconsistency in the carbon tax policy. A carbon tax is an effective way to reduce the emission of carbon dioxide. However, the effect of carbon tax in the EU has had the effect to transfer the production of goods that emit large amount of CO2 to countries that did not sign the Kyoto agreement such as the countries in the developing countries. Goods demanding use of fossil energy can therefore be produced outside the Europe and than be exported to Europe. The consequence is at best an unchanged amount of CO2 emission as it has only moved outside the EU. The consequence is loss of jobs and production capabilities in the EU with no effect at all on the global emission of CO2. As a minimum a corresponding import tax should be levied on relevant imported goods. As this has not been the case the Kyoto agreement has in this crucial aspect been a failure.
During the next 50 years the global primary energy must at least be increased by a factor of two that means that both fossil energy and nuclear energy will have to increase. The renewable energy is insufficient although not in theory but in practise. The reason is its low energy density and huge variation in time because of the weather. A central crucial factor is the insufficient capabilities of storing energy. The most positive development in recent years is the exploration of huge amounts of shale gas in the United States that is rapidly reducing the emission of CO2. A complete replacement of coal by gas will make it possible to half the CO2 emission. A similar possibility might be possible also in China that has huge amounts of shale gas as well.
We do not yet know how to best solve the Earth’s energy problems but many thing may happen in the next 100 years. A modest climate sensitivity that is supported by observations combined with a transition from coal to natural gas will provide the world with a waiting time of half a century or so but not very much longer. This will make it possible to avoid unnecessary and highly expensive panic-type subsidized investments driven by political whims and the expectations of quickly earned money and instead invest available means in a well thought through long- term energy research programs.