Topic 4 Discussions on Global Warming

8/14/2019 Topic 4 Discussions on Global Warming

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Disediakan oleh TEHTK , R&I, IPTuanku Bainun

Discussions on global warming

The discussion between skeptics and climatologists

An enormous amount of research has been conducted on the enhanced greenhouse effect. TheIPCC has brought out reports showing modelling results about expected temperature change andconsequences for the next century. There are however skeptics and scientists that argue with theresults of the IPCC. ome do not even believe that an enhanced greenhouse effect exists at all.

This page and related pages are produced by a Master student of Environmental Systems Analysis.We must note that although this material appears on our website, Lenntech is impartial and this isnot in any way a representation of our opinion. This web page is strictly of informational value.

1. The discussion on skeptical environmentalism

!"orn #omborg$ known to many as %The keptical &nvironmentalist% and named

one of the world%s '(( most influential people by Time )aga*ine$ has critici*edcurrent expectations of climate change and the consequences in his book. )anyleading experts on environmental topics have commented on this. +,-%s suchas ,reenpeace$ an organi*ation of which #omborg used to be an active member$have attacked him on various occasions see './0. !oth #omborg%s chapter onglobal warming and the reply of a leading IPCC expert are discussed here.

1.1 Bjorn Lomborg

.. !eneral

#omborg argues that %the limitations of computer modelling$ the unrealistic nature of basic

assumptions made about future technological change and political value "udgments have distortedthe scenarios being presented to the public%.

#omborg does not disagree with today%s explanation of the greenhouse effect mechanism. 1e alsodoes not deny that there must be some kind of anthropogenic addition to the greenhouse effect. 1eagrees with the idea that the centuries before '2(( where much colder than current times. 1e doeshowever mention that this is mainly because of the #ittle Ice Age$ which lasted from '/((3'2((.There is no disagreement to the so3called )edieval 4arm Period$ when temperatures were 536degrees warmer.

.." #ro$y indicators

#omborg does comment on the use of tree ring records by )ann to determine temperatures in thecenturies before the thermometer was invented. 1e argues that only +orth American tree ring datawere used and that the data only cover land surface temperatures during summer. Additionally$disturbances in measurements by other factors influencing tree ring development were notcorrected. 7ata of different origin has a lack of spatial scale coherence$ causing #omborg toquestion whether there is even enough temperature proxy data. This is an important finding$because the results of )ann%s tree ring research has already been taken up in the 5((' IPCCreport.Tree rings and other proxy indicators show changes in a '((( year period. )easurements over a'((( year period are not very accurate according to #omborg$ because evidence has suggestedthat a climatic cycle takes roughly '8(( years.

..% !reenhouse gases and temperature change
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4hen it comes to greenhouse gas emissions #omborg states that we should not ask ourselves

whether greenhouse gases emitted by human activities have an impact$ but how much effect theseemissions have on temperature. This requires an adequate prediction of climate development in the

future$ which is very hard because of the complexity of the climate system. Current computermodels are already relatively complex but do not even represent all important factors and

processes yet. cenarios pro"ections of future events0 may not always be based on reasonable

assumptions and some data may still be missing. 1ow much C-5impacts climate is stronglydependent on the representation of crucial areas in models$ such as sulphur aerosols$ water vapourfeedback and clouds. These areas are briefly explained here.

ulphur aerosols reflecting solar energy may counter the impact of greenhouse gases$ causing asmaller impact on temperature. The IPCC has admitted this and it is now included in model

simulations. This is however sub"ect to large uncertainty and it does not include other aerosolsbesides sulphur. 9urthermore$ tropospheric temperatures are an important determinant of surface

temperatures and according to satellite footage of the +-AA these do not increase as much asdepicted by the IPCC. !oth satellite measurements and weather balloon results do not show as

much warming as the outcome of climate models used by the IPCC. This difference$ if significant$would lower water feedback by evaporation and consequently lower the C-5warming. This is

because C-5warming is enhanced by water vapour$ which also traps heat. Another largeuncertainty admitted by the IPCC is how much clouds will impact temperature change. Clouds may

interfere with radiation that causes global warming and prevent ma"or temperature increases.1owever$ clouds cannot be entered in climate models in a sufficient manner yet. They therefore

represent a significant source of potential error in climate simulations. 7espite all these remarksconcerning the impact of C-5emissions on temperature$ the IPCC predictions of temperature

change were hardly altered in the past '( years.

..& 'ther causes of temperature change

#omborg also states that we should ask ourselves whether greenhouse gas emissions are the realcauses of temperature change. It is the question whether temperature change really leads to thecatastrophic events that have been predicted by the IPCC models.It is important to mention that not only greenhouse gases$ but also solar energy impacts globalwarming. The debate on global warming has had the tendency to only focus on one out of twofactors. The IPCC mentions solar energy only briefly. #omborg states that it is possible thatincorporating solar activity will also lead to a lowering of the estimates of the C-5warming effect.olar brightness has increased over the past decade$ increasing temperature by an estimated($/oC. A recent study showed that direct solar radiation has caused about /(: of the observedglobal warming of the past 6( years. 7anish meteorologists have pointed out a clear connectionbetween the duration of the solar cycle and average temperature on earth. This theory is stillargued. ;esearch that was conducted so far has shown that longer solar cycle duration resulting inlower solar activity. This leads to more cosmic radiation and increases cloud formation. Thesecosmic rays produce low3level clouds from ions which reflect solar energy$ preventing warming ofthe earth%s surface. This theory also states that shorter solar cycles lead to higher surfacetemperatures according the the reverse mechanism. This apparently explains temperature changes

from 'oC0.

..( )#** scenarios

#omborg has some concrete comments on the scenarios made in '225 by the IPCC. 1e states thattheir predictions of population growth may be too high$ as they are much higher than those of the?+ today. 1e also disagrees with their expectation of


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In the new scenarios constructed in '22= the IPCCabandons the idea of predictions and starts

using the term pro"ections. The emissions estimates for sulphur dioxide in different scenarios arenow lower than those made in '225. This has an important impact on the greenhouse effect

because sulphur aerosols in the atmosphere may decrease global warming$ as was explainedbefore.

The IPCC scenarios with a sustainable way of living seem to score much better than the wealthy

scenarios. !ut according to #omborg we must ask ourselves if transferring to a sustainable world asdepicted in the scenarios is really worth it$ as it means that our children may earn only 8(: of ourcurrent income. This is a central question in dealing with global warming.

#omborg finds the energy improvement in the sustainable scenarios a bit peculiar. This is becausehigh energy use in the wealth scenarios should eventually drive up energy prices$ so that the

difference between energy improvement between the scenarios might actually not be so high. -neof the wealth scenarios shows a remarkable transfer to renewable energy sources. This price

increase could be the reason for that. 1owever$ #omborg wonders if the prices for renewableswould ever decrease so much that they would actually be cheaper than fossil fuels. )ost IPCC

scenarios do assume this$ or even assume that mere environmental concern will cause the transfer.#omborg advises an actual analysis of the extent to which fossil fuels would be replaced by

renewables$ and why. 1e wants to know how likely the transfer towards more sustainable scenarioswould be$ but this is not treated to a great extent by the IPCC as they regard all scenarios as likely.

A model made by political economists determined that the prices of renewables are alreadydecreasing by 6(: per decade and they may even be competitive by 5(/(. This result causes the

scenario where fossil fuel use continues to rise to be rather implausible. The model also calculateda higher actual global temperature change than was pro"ected by the IPCC.

..+ *onseuences of global warming

)any consequences of global warminghave been predicted and modelled by the IPCC. Inagriculture a severe decrease in crop yield is expected which will eventually cause overallproduction to fall. !ut #omborg finds that even the most pessimistic evaluation of ?@ )et -fficeexperts expects crop production to grow dramatically over the next 8( years$ so that overallproduction will not fall. )ost plants grow better at higher atmospheric C-5concentrations andhigher temperatures$ because of an enhanced fertili*er effect. This effect will cause productiondeclines to be much smaller. ,lobal warming may enhance the difference between developed anddeveloping countries$ because developed countries can ad"ust their farming methods moreeffectively and a longer growing season may not have as much of a negative impact. 1owever$ bythe time the impact of global warming will be visible developing countries may be much moredeveloped. The IPCC scenarios are only based on current development records. The IPCC also doesnot take into account the possibility of development of stronger crop varieties resistant to globalwarming impact.,lobal warming has often been connected to sea level rise and melting of polar ice caps. Indeed$the sea level has risen '(358 cm in the past century and will continue to rise by a further 6'3/2 cmin the next century. Three3fourths of this rise is a result of water expansion by warming and theother fourth is because of ice cap melting. According to the IPCC sea level rise will expose >(35((

million more people to flooding in the next century. !ut #omborg mentions that one cause for theincrease in people living on flood plainsis growing population. 1e also emphasi*es that as the world

becomes richer we may be able to afford more effective0 measures to decrease the number of

people exposed to flooding. This is not included in the models$ which only concern measures thatare already taken today. #omborg also expects that the costs of flood protection will eventuallydecrease.

It is often said that global warming will put human health under pressure$ particularly that of urbanpoor and elderly with no air3conditioning. According to #omborg however$ we must take into

account that a richer world will give more people access to air3conditioning. In a warmer world alsofewer people would be dying from cold weather$ which has a much higher death toll than warm

weather. A recent study of populations in &urope showed that people can ad"ust successfully tosmall increases in summer temperatures. This leads #omborg to believe that populations are likely

to ad"ust to changing temperatures consequential to global warming. )oreover$ the decrease inwinter deaths would outweigh an increase in summer deaths$ according to him. It is also argued by

the IPCC that certain diseases such as )alaria will increase in warmer weather. According to#omborg this is not only the case in warmer weather$ as )alaria was a ma"or epidemic far into the

Arctic Circle throughout the #ittle Ice Age$ because mosquitoes would hibernate in sheltered sites.-nly building techniques and better medicine could rid people of )alaria after the #ittle Ice Age.

&ven though the global area of )alaria could be expanded$ development and resources could force
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back epidemics. Actual )alaria transmission would undergo little change as a result of global

warming$ because most newly exposed would come from richer countries where there is sufficientmedicine.

,lobal warming is said to increase the number of events of extreme weather$ leading to extinctionof some endangered species. There have been periods in the 1olocene when temperatures were '3

5 degrees warmer and no extreme weather occurred. Computer models have given inconclusive

results when it comes to extreme weather. ome models do predict it$ while others predict nochange at all. The IPCC states that only on a regional scale clear signs of extreme weather havebeen found$ but these patterns are also inconclusive in climate variability. There appears to be no

clear evidence supporting the occurrence of extreme weather events. #omborg states that claims ofmore extreme weather that are meteorologically unsubstantiated are often backed3up by an

economic observation of increasing weather3related costs. It is however unclear if this directcomparison of costs is reasonable. It ignores increasing population and more people that are

moving to coasting risk3prone areas. A '222 study showed that extreme weather events were notthe main cause of catastrophes in the '22(%s. ocietal changes are a much more likely cause.

+ot all temperatures have changed. ,lobally$ minimum night temperatures are most likely toincrease. )ore warming has taken place during winter than during summer. Consequentially only

Australia and +ew ealand had their maximum temperature go up. This may cause agriculturalyield to increase. These temperature changes might increase the number of days of heavy rainfall.

9looding may occur as a result$ but this will probably be prevented by future measures$ such aswetland conservation and dam construction. The combined increase in temperature$ C-5and

precipitation will make the earth greener. IPCC models have also pro"ected this change.

#omborg states that it is important to decide what considerations we should employ to determine

whether or not and how we should take action. +o matter what we decide$ it will be a costlyoperation. And all measures should be based on reliable evidence$ which is hard now that we still

rely on inadequate model data. These considerations will cause the global warming debate tocontinue far into the future.

..- *osts of yoto

The IPCC has estimated the costs of global warming by aggregating the total cost if C-5

concentrations would double instantly and than stabili*e. #omborg comments that this is not likelyto occur and that this cost estimate does not take into account possible future adaptations toclimate change. 1e also states that the higher end of the IPCC estimated range of temperature rise'$/38$


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future for @yoto to actually have an impact on global warming.

The costs of @yoto can be shared more effectively by trading emissions permits. This basicallymeans that emission cut3backs are performed by the country that generates the lowest cost. This is

made possible because it is argued that it does not matter which country emits greenhouse gases$because dispersion in the atmosphere will cause the impact to be noticeable worldly. 9ree trade

would cause countries that trade permits to both be better off. 1owever$ the &? rather wants its

own countries to trade amongst themselves$ whereas the ? votes for a larger degree of trade. Thetrade mechanism largely determines @yoto costs. A global trade mechanism generates least costsand no trade at all is most expensive.

#omborg also argues that a C-5emission cut3back of 8$5: is very high$ because it is a cut3backcompared to '22( levels. This also means that the necessary cuts will increase and eventually they

must be 8(: by 5(8(. This causes an increase in @yoto costs because higher cuts will costs moreand more money. #omborg states that this will cause emission cuts in 5(8( to be about equally

expensive as global warming in 5'((. And these costs must still be paid according to #omborg$because @yoto will only postpone temperature rise$ rather than prevent it. This would mean that

countries pay the double price for global warming.

../ Action or inaction

9inally$ #omborg emphasi*es that we need to be careful in our choice of how to act. 1e claims thatif we reduce C-5emissions more than '': or stop using fossil fuels totally$ this will cause greateconomic losses. Apparently the optimal policy calls for a relatively modest level of control of C-5.#omborg states that it would be better to simultaneously invest in cleaner technologies such assolar power. 1e also wonders why reports on global warming do not treat the consequences ofma"or emission cut3backs for the economy and society. If the costs of cuts outweigh the eventualcosts of global warming$ economy may be negatively affected. #omborg admits that we can affordthe cut3backs$ but he wonders whether postponing ,7P growth for a couple of years after 5(8( isreally worth it.

ource #omborg$ !.$ The S0eptical Environmentalist 1 Measuring the 2eal State of the World.Cambridge ?niversity Press '22


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mean that a wider range of costs is possible$ which is also mentioned by the same economists cited

by #omborg.#omborg does cite a range for climate policy costs. This is however based on the findings of

economists only$ whereas it fails to take into account pre3existing market imperfections. 4hen asociety takes away these imperfections it may actually reduce emissions costs substantially.

chneider is unhappy about #omborg%s dismissal of the @yoto Protocol. 1e states that it is not

possible to extrapolate the protocol from 5('5 to 5'(($ as #omborg has done in his work. The IPCCreport mentions that eventual emissions cut3backs should be up to 8(:. #omborg finds this veryhard on economy$ but chneider replies that only @yoto cannot achieve this. !oth developing and

developed countries will have to fashion cooperative and cost3effective solutions over time.#omborg thinks that international cooperation is still too narrow for @yoto to actually make a

difference$ but chneider replies that when it comes to international cooperation$ @yoto actuallycould be a first step that may not be dismissed so easily.

In general$ chneider comments the subtitle of #omborg%s bookB %The real state ofthe world%$ because the IPCC has clearly shown that the real state of the world will

not turn out as fine as #omborg describes. It may be within any of the proposedscenarios$ but both the IPCC and #omborg cannot be sure of how the future will

unfold. 1e also comments the Cambridge ?niversity press for publishing an un3reviewed work.

1. Lomborg replies

!"orn #omborg states that many of the arguments used by chneider are incorrect. 1e finds thatthe information he used is of fine quality because he has taken it from top international worldorgani*ations and existing statistics. 1e does not state that things will all be fine as chneidermentions$ but rather that we should not act on myths of doom as they are sometimes representedabout global warming and its consequences.#omborg replies that he does not deny that global warming and the anthropogenic contribution tothis phenomenon exist. 1e uses IPCC information and is of the opinion that he has notmisrepresented this.According to #omborg other scientists have stated that chneider cited secondary literature whenhe tries to undermine #omborg%s arguments. Ironically this is exactly one of the arguments

chneider initially used against #omborg.#omborg repeats his argument that we should not necessarily act on global warming$ as ourinstincts tell us to do. ;ather we should carefully weigh the costs of action against those of inactionand than decide whether and how we should respond.1e also repeats his argument of @yoto being to costly for all the good it does. 1e finds that it maybe better to assist developing countries in their development$ in order to increase sustainability. 1ealso states that chneider neglects to mention all the extra costs that would be generated byeventually expanding @yoto to a 8(: decrease in greenhouse gases. This would be at the cost ofour capability to deal with other environmental problems.

ource The Scientific American$ 5(('. 9or the full reply by #omborg see httpDDwww.lomborg.organd for other replies by authors$ see httpDDwww.sciam.comDsearchDindex.cfmEFTGFHCCGFHFGlomborg

1.4 Greenpeace vs. Lomborg

)iraculously enough$ !"orn #omborg used to be an ecological activist andmember of the international environmental organi*ation ,reenpeace. 4hen hepublished his work %The S0eptical Environmentalist% ,reenpeace highlyprotested its content. They gave him the title %Anti3Christ of the ,reen;eligion%. ome campaigners have even taken it to the point where they call#omborg %an intellectual fraudster who is motivated by a fascistic desire todiscredit the environmental #eft%.

+ot only ,reenpeace protests #omborg%s views. As was shown above$ scientists also try to discredithim. tuart Pimm and eff 1arvey in +ature maga*ine

JThe te$t of The S0eptical Environmentalist on global warming and climate change employs thestrategy of those who, for e$ample, argue that gay men aren3t dying of A)4S, that 5ews weren3t
http://www.lomborg.org/http://www.sciam.com/search/index.cfm?QT=Q&SCC=Q&Q=lomborghttp://www.sciam.com/search/index.cfm?QT=Q&SCC=Q&Q=lomborghttp://www.lomborg.org/http://www.sciam.com/search/index.cfm?QT=Q&SCC=Q&Q=lomborghttp://www.sciam.com/search/index.cfm?QT=Q&SCC=Q&Q=lomborg


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singled out by the 6a7i3s for e$termination, and so onJ.

#omborg has written a chapter on global warming that questions the seriousness of the problemand critici*es our methods of dealing with it. This does not mean #omborg does not believe a

greenhouse effect exists. In other chapters however$ he takes matters one step further by claimingcertain environmental problems really are not as serious as we think and acting on it as we do

today may be unnecessary. 1e claims that the world is not running out of resources and speciesare not rushing to extinction at the rate that is claimed. ,reenpeace highly contests this view.

#omborg claims that ,reenpeace misrepresents his views by claiming he states that everything isgetting better. ;ather$ he states that some environmental problems are not as serious as we think

compared to past levels and that we need to get a sense of priority.

#omborg%s thesis is not meant to be anti3environmental. 1e simply wants to point out thatenvironmental protection today is based to much on scaremongering and ideology$ whereas itshould be based on rational analysis and risk3assessment.

The 7aily Telegraph calls #omborg %a marked man%$ because of threats he now receives fromenraged environmentalists consequential to the claims in his book. In eptember 5((' oneenvironmentalist even hit #omborg in the face with a baked Alaska pie for claiming Arctic wildnessis not dying out.

ource Thomas$ 7.$Anti1*hrist of the !reen movement$ 7aily Telegraph 5(D'D5((5

2. The three that call climate change a 'dogma'

#abohm$ ;o*endaal and Thoenes from the +etherlands have written a book on

global warming that discusses current scientific evidence for the greenhouseeffect. The writers of this book are so3called climate skeptics that take the

discussion even further back than !"orn #omborg didB they doubt the veryconcept of anthropogenic global warming. They also believe @yoto to be

insufficient and expensive and believe the scarce sources used for this protocol

could be used for better purposes. In their prologue$ they state that globalwarming is a topic that requires wider discussion and should not be dealt withsolely by experts. They also call for the inclusion of a wider scientific audience in

the research. They even discuss religious values and the impact on people%sclimate change beliefs. They simply start by stating the facts on global warming.

2.1 !acts

C-5and other greenhouse gases can trap heat and thereby enhance the greenhouse effect. Thisheat3trapping may result in warming but this is a hypothesis$ not a simple truth.C-5concentrations have risen substantially in the past '(( years and especially in the pastdecades. It is plausible that anthropogenic emissions have caused this increase. everal estimatesstate that anthropogenic contribution to C-5emissions is less than 8: of the total production.

2.2 Assertions

The writers state that a substance so crucial to all life forms would not be likely to cause climate

change beyond what naturally occurs in the climate system. They think that it has been greatlyexaggerated in order to safeguard donations of people to environmental organi*ations that depend

on them. All media attention the greenhouse effect has received has given green parties andenvironmental +,-%s the opportunity to keep convincing people to support them.

The writes argue that scientists manipulate data to generate a certain outcome. They give theoutcome of the Club of ;ome research as an example. This result stated that people in rich

countries were consuming too much food and we would soon run out. -ne of the assumptions inthe computer model that was used was apparently that each family had / children$ whereas an

assumption of 6$6 children produced no food crisis forecast at all. The writers argue that the figureof / children was selected on purpose. This also is an example of the incapability of computer

models. &ven on the most sophisticated computers$ it is argued$ climate complexity would far


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exceed their capabilities. This results in much of the climate excitement being based on computer

models that are still too crude. There are large uncertainties in the models$ for example when itcomes to the role of clouds in the climate change system.

The writers also mention the lack of temperature data as a result of the late invention of thethermometer. -nly &ngland has temperature data of one region that dates back all the way to

'=82. The record shows that a warming trend of ($


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tephen )cIntyre and ;oss )c@ritick have contradicted theso3called %hoc0ey stic0 theory% founded by )ichael )ann.

According to this theory current temperature rise is uniqueand the chart of temperatures in the past decade is shaped

like a hockey stick see figure0.

This chart was the result of tree ring records$ coral ice coredata and historical records$ which were used to determinetemperatures over the past = centuries. It was included in

the IPCC 5((' report.

The two )c%s went through the same database )ichael )ann and others had used for the earlierpaper and used a similar calculation. 1owever$ the outcome was completely different and led to thebelief that )ann and others manipulated their data. According to their calculations the '8th centurywas warmer than the 5(th century. They stated that )ann%s records contained % collation errors$un"ustifiable truncation or extrapolation of source data$ obsolete data$ geographical location errors$incorrect calculations of principle components and other quality control defects%.)ichael )ann and his colleagues claim that the )c%s have not carried out a proper audit of theirresults. According to )ann the same data was not used and their exact procedures were notfollowed. 1e was so far not given the opportunity to really respond to the )c%s critique on his data.

This discussion is therefore far from over. The )c%s have already announced they will soon publisha new critique.

The theory of )ann was also contested by #omborg see earlier0. #abohm$ ;o*endaal and Thoenesuse similar arguments to discard the theory. Kon torch has attempted to reconstruct currentclimate by entering )ann%s tree ring record into a climate reconstruction model. The reconstructionappeared far from correct. !radley and others commented in Sciencethat )ann had too fewcalibrated data for the tropics and the southern hemisphere. This makes the extrapolation of theresults to global scales implausible.

This critique on )ann%s records does not necessarily mean that the theory of current climatechange being unique and therefore anthropogenic is disregarded. The evidence is still too narrow toreally alter our beliefs. -ther scientists have also shown current warming patterns to be unique and

so far they have not been proven wrong by the skeptics.

ources

3 #abohm$ 1.$ ;o*endaal$ . and Thoenes$ 7$ Man1made !lobal Warming8 9nraveling a 4ogma.

)ulti3cience Publishing 5((/$ &ssex$ ?nited @ingdom

3 +;C 1andelsblad$ = februari 5((8 %:errie om een :oc0eystic0%

%. $ark $aslin on what skeptics sa#

)ark )aslin is the author of %!lobal Warming, a very short introduction%$ a

book written with the sole purpose of informing people about global warmingand the greenhouse effect. In his book he reviews and critici*es what skeptics

say about global warming.

%.1 &2( cause or conse)uence*

ome skeptics claim that ice3core data suggests that global C-5responds to global temperature.They therefore conclude that C-5is a consequence$ rather than a cause of global temperaturechange. )aslin argues that examination of ice3core C-5data suggests that increases in

atmospheric levels occurred at the same time as the gradual warming in Antarctica. tep3wisewarming of the northern hemisphere occurred in a later period. Time3series analysis by a professorof Cambridge ?niversity has pointed out significant atmospheric C-5levels 8((( years before


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global variations in ice caps. All this evidence leads )aslin to believe that global C-5levelsincreased before overall global temperature rises and ice cap melting.

%.2 Data manipulation

A well3known and often recurring critique of skeptics is that global warming data is manipulated togain a desired outcome. This causes many discussions on whether global warming really exists.

#abohm et al. have for example used this argument see above0. )aslin argues that this is amisunderstanding that is created because all global warming data requires some ad"ustment. +ot

all insights into data sets concerning global warming were immediately present. Accordingly$changing the data sets is all part of the scientific process. Constant questioning of the data adds to

the confidence climatologists have in their results. The IPCC tries to make sure they verify theirresults by checking them through different studies and by using very different sources.

%. Solar activit#

!"orn #omborg is one of the skeptics that mentions that solar activity$ not C-5concentrations$ is

mainly responsible for past temperature ranges. !oth skeptics and non3skeptics agree that this hassome impact. cientists state that not only solar activity but also volcanoes have an importantimpact on past temperatures. 1owever$ )aslin states that the skeptics may put too much weighton the solar activity hypothesis. &ven though there are still some ma"or uncertainties in this area$ itis clear that a combination of solar activity and greenhouse gas concentrations together have beenable to simulate a global temperature curve for the past '6( years. )oreover$ evidence suggeststhat solar activity and volcanic eruptions have been similar for the last millennium. This means thatnot only natural forcing causes global warming. An anthropogenic effect by greenhouse gases iscertainly present.

%.% Satellite data

atellite data has suggested that over the past two decades there has been a slight cooling.1owever$ re3examination of data and examination of the source demonstrated that there are some

inconsistencies in satellite data. Altitude ad"ustments$ friction with the atmosphere and inter3instrumental comparisons casted serious doubts about whether the obtained data were consistent.

)oreover$ two decades is too short a time to find any usable temperature trend. Al temperaturecycles together take much longer than 5( years. 4hich of the cycles is present at the time of

satellite operation remains to be seen.

%.+ &loud ,eedback

Clouds can have both a positive and a negative feedback on global warming. keptics have claimedthey may reduce the impact of global warming to a negligible amount. The role of clouds in theclimate process is still one of the ma"or uncertainties acknowledged by the IPCC. Clouds can both

absorb and emit radiation$ thereby either cooling or warming the surface. 4hich of the to effectstakes place is largely dependent on the location and characteristics of clouds. This largely dependson the atmospheric distribution of cloud forming particles. Cloud representation in climate modelshas improved$ yet uncertainties still remain. Climate models so far have shown that the coolingeffect of clouds does not have a large enough impact to counter global warming trends.

%.- &limate model reliabilit#

A question that has been asked by skeptics many times is whether or not we can trust climate

models. Climate models often give different results$ they fail to predict abrupt weather conditions$they fail to reconstruct natural variability$ deep ocean circulation and past climate trends and proxy

data may be more extensive than model outcomes.)aslin argues that science is not a discipline that will predict the exact future$ even though people

often seem to expect this. trangely enough we do not expect this in any other discipline. +oclimate model is ever exactly right$ but they do provide our best estimate of future events. )any


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different models have predicted roughly the same future temperature trend so far. This strengthensour confidence in the models$ which have been built by many different scientists from all over the

world. )aslin emphasi*es that if models would provide an exact prediction of the future$ no onewould believe it. It would still lead to the same discussions we face today.

keptics feel that abrupt changes in the weather have an impact on our climate. !ut climatemodels cannot predict these abrupt changes because of a too course spatial resolution. !ut these

abrupt changes only impact weather forecasts. #onger3term trends in regional and global climateare not impacted by short3term changes in weather conditions. It is however true that we cannot

model abrupt climate changes$ yet.The reconstruction of natural climate variability has become increasingly good. The reali*ation that

these variations significantly impact regional climate has caused scientists to include them inclimate models. The confidence level of simulations of natural variation is not yet very high.

1owever$ constant improvements cause better and better predictions on this part.7eep3ocean circulation has been included in climate models from the very beginning and it

therefore can be predicted with a relatively high level of confidence. 1owever$ deep3oceancirculation is a very complex process and therefore uncertainties remain in predictions of future

occurrences. This may be fixed in the future as climate models evolve.Climate change data from climate models is narrower than climate change suggested by proxy

data. Comparison has demonstrated that model outcomes are about >8: correct. )odels may

therefore systematically underestimate climate changes. )aslin concludes that climate change mayvery well be at the top end of current estimates.

ource )aslin$ ).$ !lobal Warming, a very short introduction. -xford ?niversity Press$ -xford

5((/$ page =(3=8$ >


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concentrations has admitted that the assumptions about methane of the IPCC were based on anunderstanding of methane build3up that was five to '8 years old. This may explain the differencesbetween IPCC and +-AA scenarios.

ource +ational -ceanic and Atmospheric Climate Administration +-AA0

-. Speci,ic data discussions

All data that are produced on global warming are discussed on many occasions as this continues tobe a topic sub"ect to large uncertainties. ome of the current discussions are mentioned here.

-.1 Documentation o, temperature measurements

Critics have claimed that average earth temperatures may not be accurate because there can be

local variations around the world of up to '(( degrees between two locations. This means thataverage global temperature can only be valuable when it is expressed as an anomaly$ for example

the difference between the current average global temperature and a period of reference$ being the

last 58 years for example. !ut even these anomalies are lacking in precision.To measure global average temperatures in 5((( rectangles of 8 degrees longitude and 8 degreeslatitude are applied. 1owever$ not all rectangles contain measuring stations and therefore many

average temperatures are estimates from neighbouring rectangles. o far a more accurate methodhas not been developed. To include local temperature variations in the global average temperature

at least one station in every '(x'( km would be required. This would mean more than 8 millionmeasuring stations evenly distributed across land and oceans$ whereas in reality there are only

8((( measuring stations currently.The temperature measurements over the past century were very inaccurate. Critics point out that

not all thermometers were good and that measurements were only conducted on land$ whereas theearth consists of >(: water. Also$ measurements were largely conducted in urban areas$ where

houses increase warmth in their direct environment this can be a '35oC0.

ome of these critics argue that satellite measurements of earthtemperatures may be more accurate because they cover the entiresurface. ;elative accuracy of satellites appears to be small. The IPCCdoes not agree with these arguments$ because inconsistencies in satellitedata$ as was pointed out by chneider see earlier0.

ources

3 #abohm$ 1.$ ;o*endaal$ . and Thoenes$ 7$ Man1made !lobal Warming8 9nraveling a 4ogma.)ulti3cience Publishing 5((/$ &ssex$ ?nited @ingdom

3 Karious internet articles

-.2 &2emissions and temperature change

Astrofysica allie !aliunas claims that at least


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#abohm et al. state that C-5only absorbs infrared radiation in a small part of the spectrum. They

therefore doubt that an increase in C-5content would have a significant effect on the heat balanceof the earth. They claim that the comparison of the earth to a greenhouse is un"ust because the

earth system is much more complex than simply an incoming and outgoing flow of radiation. )anyfactors may positively or negatively influence this flow and it may come from different angles. A net

radiation in a region therefore does not automatically mean that temperatures will rise. In the IPCC

reports this mechanism$ known as %radiative forcing% is stated true. According to the writers thisconcept is fundamentally wrong. They also state that no significant temperature rise has beennoted in the past >( years$ whereas C-5concentrations have significantly increased. They do not

consider climate change unlikely$ but they doubt whether it will always manifest as a change intemperature.

3elated pages

Climate change glossary

;ead more httpDDwww.lenntech.comDgreenhouse3effectDglobal3warming3

discussion.htmL,reenpeaceLix**(t/1e=K>F
http://www.lenntech.com/greenhouse-effect/climate-change-glossary.htmhttp://www.lenntech.com/greenhouse-effect/global-warming-discussion.htm#Greenpeace%23ixzz0t4He6V7Qhttp://www.lenntech.com/greenhouse-effect/global-warming-discussion.htm#Greenpeace%23ixzz0t4He6V7Qhttp://www.lenntech.com/greenhouse-effect/climate-change-glossary.htmhttp://www.lenntech.com/greenhouse-effect/global-warming-discussion.htm#Greenpeace%23ixzz0t4He6V7Qhttp://www.lenntech.com/greenhouse-effect/global-warming-discussion.htm#Greenpeace%23ixzz0t4He6V7Q

Topic 4 Discussions on Global Warming

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