1. Summary and Conclusion
Carl Denef, January 2014

2. Despite the threat of the climate crisis, global emissions of CO2
are set to rise again in 2013, reaching a record high of
36 gigatonnes.
Gigatonnes C02

3. Overview of past, present and future climate
change
Era Global average temperature
anomaly
Atm. CO2
(ppm)
Sea level vs
preindustrial
In 2100 (RCP8.5 scenario) 2.8–5.5 ºC vs preindustrial 1200 0.5–1 m
Present 1.5 ºC vs preindustrial 395 0.3 m
8.2 ka event 2–3 ºC in 2 decades 275
Younger Dryas 7-8 ºC in 1 decade in Greenland
and N-Atlantic, followed by abrupt
250
D-O events 4–6 ºC in decades from ~200 to 220
Last Glacial Maximum 3–8 ºC vs preindustrial 190 120 m
Last Interglacial 1–2 ºC vs preindustrial 280 5.5–9 m
Less Greenland ice sheet
MIS-11 Interglacial 1.5–2.0 ºC vs preindustrial 280 6–20 m
No Greenland ice sheet
Older interglacials 2 ºC vs preindustrial 250-280 = preindustrial
Mid-pliocene 3–10 ºC vs preindustrial 365-415 7–20 m
No Greenland ice sheet
PETM 4-7 ºC vs preindustrial
Sea surface temp.Tropics = 35 ºC
Polar temp. = 10-20 ºC
1125 100–200 m
No polar ice sheets

4. Summary and Conclusion
 The present slide show depicts a critical geopolitical issue that humanity had never to face at
a planetary scale.The issue is climate change and its impact on human civilization. Is it true
that climate is changing today and what will climate bring to future generations? What are the
causes and mechanisms? Can the change become dangerous or catastrophic and when? Can
dangerous climate change be prevented or reversed?
 Science is convincing, climate is changing across our Planet and the change is largely due to
human activities. The change is detectable in all components of the climate system: warming of
land and sea surface,increase in ocean heat content, retreat of land and sea ice, sea level rise,ocean
acidification,and weather extremes. Certain regions become wetter,while others dryer. Global
warming means a rise in the yearly average surface temperature over the globe (1.5 °C since the
end of the 18th century) and an increase in the number of very hot days. In a warmerWorld,certain
regions can temporarily be colder than normal for that location, but at any given time areas with
higher temperatures exceed by far the areas with a temperature lower than normal. There is
no place on Earth where average yearly temperature is decreasing with statistical significance.
 Although natural processes often changed climate during Earth’s history,they cannot explain the
present changes, nor can changes in solar radiation be invoked.The present change is caused
primarily by an ever-increasing fossil fuel consumption and deforestation during the Industrial
Era,which enhanced the concentration of greenhouse gases in the atmosphere and of black
carbon dust at a rate much faster than the Earth can recycle.According to the laws of physics, the
consequence is increased longwave radiation, resulting in warming. Global warming,in turn,
causes melting of ice, sea level rise and extreme weather events. CO2 is the primary anthropogenic

5. warming factor,followed by methane, black carbon dust and ozone. The actual level of CO2 in the
atmosphere is ~400 ppm, which is 43 % above the preindustrial level of 280 ppm. Empirical data from
today and the past, and simulations in climate models have shown that doubling atmospheric CO2
results in a 2.6–4.1°C global warming.This is ~3 times more than expected from CO2 alone,because
radiative forcing of the latter is enhanced by water vapor,clouds, and ice sheet feedbacks.
 Climate change is modulated by natural variability.El Niño augments the warming rate,while La Niña
attenuates the trend.The last decade may have experienced less warming due to more La Niña, a small
decrease in solar radiation (sun spots),increased vulcanic aerosols and a recent cooling in the
eastern equatorial Pacific.
 Climate change is characterized by the phenomenon of inertia, commitment and irreversibility. It
takes several decades before warming of a given amount of CO2 is realized but the change is
committed to appear and to remain for at least 1000 years once established.
 Although negative impacts of climate change are already being seen today, they do not frighten people
yet in large parts of theWorld, but people will inevitably become frightened by the end of this
century. Large ensembles of climate models predict that, in the worst case scenario of continuously
increasing fossil fuel use (RCP8.5 scenario),average global temperature would be ~4 °C higher in 2100
relative to 1990. Average land surface temperature would be 6°C higher in theTropics and Subtropics.
That means that in those regions average temperature over land would be 26-36 °C instead of 20-
30°C today.Temperature extremes will be up to 11 °C higher than now and will occur more
frequently all over theWorld.Cities will experience even more warming as they heat more than the
v

6. surrounding land. By 2300 average global temperature would be 8 °C higher, with an upper
bound of 10 °C. Since the limit of sustained wet bulb temperature*,above which the human body can
no longer adequately cool, is 35 °C, and since a 10 °C rise in average surface temperature may
result in a wet-bulb temperature of 35 °C in many tropical and subtropical regions,where more than
40% of Earth`s population lives, a worst case scenario warming (RCP8.5) will have strong and
widespread devastating impacts on human society by 2300. Moreover,much of this warming will
persist for more than 1000 years,even if emissions are set to zero at that time. On top of this, sea
level rise, storms, droughts,wildfires,floods, climate refugee problems and food shortage will
exacerbate the situation.
 Will climate change become catastrophic?
In assessing the severity of future climate change several observations appear to argue against a
catastrophic development. 1) Sudden warming or cooling events of a similar magnitude as that
projected now under an RCP8.5 scenario, occurred often during the last Ice Age and during the
transition to the Holocene.Temperature change occurred sometimes even at a faster rate than today.
Nevertheless,Homo Sapiens evolved and spread over the globe during these harsh climate changes,
suggesting that rapid warming or cooling is not incompatible with human development.
Moreover,modern humans have scientific and technical capabilities for adaptation that our ancestors
did not have. 2) Under a 4 °C warming scenario, sea level rise will force people to be displaced and
migrate,but his process will be gradual over 2000 years and is limited to 10 m, allowing time to
adapt. 3) Reconstructions of palaeoclimates have shown that, millions of years ago, surface ocean pH
* Wet bulb temperature is the temperature indicated by a moistened thermometer bulb exposed to the air flow. If relative humidity is 100%,
wet bulb temperature equals air temperature. The lower the humidity, the higher the difference between both.

7. was 7.4 and then increased to the present value of 8.2.This suggests that ocean ecosystems might
adapt to a more acid ocean than that today.
The above assumptions,however, are misleading for several reasons. 1) Models predict that the upper
limit of viable temperature for humans (wet-bulb temperature of 35 °C) will be reached in regions of
theTropics and Subtropics if there is a 10 °C rise of the average global temperature (air
temperature).This temperature rise is not impossible under the RCP8.5 worst case scenario,
although it will probably not be reached before 2300. 2) Although there have been palaeoclimates,
such as the PETM and the EECO,with similar high temperatures,fossil data indicate that mammals
at those epochs were small (average 1 kg),making their surface to body mass ratio larger,hereby
improving their body cooling and hence enabling them to tolerate higher temperatures. Moreover,
anthropogenic warming today and in the future is at a much faster pace than during the PETM epoch,
making adaptation through biological evolution very unlikely. 3) A 10 °C warming will likely also
melt the Antarctic ice sheet, which would raise sea level by at least 50 m. 4) As to ocean pH,it
remains uncertain over which time scales biotic adaptation is feasible.Moreover, acidification acts
in synergy with the decline of oxygen and nutrient in the oceans, creating non-linear adverse
effects on ecosystems. 5) Last but not least, future climate change impacts may act in
synergy with other anthropogenic impacts. Human consumption of the Earth’s resources has
now reached levels exceeding the capacity of the Earth to regenerate several of these resources.[Ref]
These human impacts not only risk to cause shortages in food and materials supply but also to
deteriorate wildlife habitat and ecosystems. Since wildlife and ecosystems services are vital to human
life,their loss, in combination with climate change,could become disruptive to human existence.
Moreover,due to the global connectedness of ecosystems and economies, impacts in one place

8. can rapidly spread and cause instability in many other regions around theWorld. Finally,the
distribution of climate risks is very uneven, being greatest in the poorest countries which also are
the least responsible for greenhouse gas emissions. Inequity threatens political and social
stability, which may become flashpoints for ecological and human disaster. Thus,if temperature rise
remains unabated,climate change has the potential to become catastrophic by the end of this
century and even make large parts of the Planet inhabitable for humans by 2300.
 What should be done? Since the main cause of global warming is radiative forcing from the ~500
gigatons CO2 that humans releasedin the atmosphere,the direct solution is removing CO2 and
lowering global temperature by solar radiation management.Theoretical and small scale
methods exist but the efficacy, permanency and safety of these methods at a planetary scale remain
unsufficiently known.Until climate change can be fixed we ought to adapt to the change by building
resilience against climate impacts and reduce CO2 emissions to mitigate the aggressiveness of
climate in the future.The dominant current approach is stabilizing CO2 in the atmosphere at the
presumptive safe level below 450 ppm.This is believed (but not proven) to limit global average
temperature rise to 2ºC above preindustrial level and to keep it at that level. However,in
order to attain this target,a ~70 % reduction of greenhouse gas emissions is needed
worldwide by 2050 and low carbon renewable energy facilities should largely replace fossil fuel
energy.Emission cuts are also necessary to fix the serious health issue caused by pollution from
fossil fuel burning.
 Not to forget, cutting emissions will not reverse committed climate change and in case we fail to
meet the 70 % emission cuts rapidly,temperature will continue to rise.The longer it takes to

9. stabilize climate,the higher the chance that unforeseen climate feedbacks may develop,creating new
problems with potentially more dangerous consequences.Therefore,much more research attention
should be devoted to CO2 removal technology, solar radiation management and
strategies of adaptation to a warmerWorld, particularly since it is not for granted that stabilizing
atmospheric CO2 at 450 ppm is a safe bound. Indeed,during the Pliocene epoch CO2 levels were
similar to present levels, yet, average global temperature rose 3-4 °C, not 2 °C as anticipated now.
Another effective measure for cooling the atmosphere could be the drastic reduction of non-
CO2 greenhouse gas and black carbon emissions as the residence time of these substances in
the atmosphere is relatively short,resulting in more rapid cooling once they lower.
 What is the prognosis of success? Various measures to reduce greenhouse gas levels have been
implemented worldwide. However,global initiatives, such as the Kyoto protocol and UNFCCC
agreements,are still far removed from what is needed to meet the 2 °C target.Reticence and
inertia of governments and the general public impede progress. As the climate problem is
unprecedented, there is no experience to rely on.The average citizen does not feel responsible or is
locked in the existing consumer and individualistic society. Government decisions are often
dominated by particracy. Although the free market easily got global,the nationalistic reflex of self-
preservation still prevails over a global cooperative approach to the climate problem. Climate
mitigation efforts,such as the carbon credit system, are often misused. There is malicious
misleading by big companies that fund the undermining of climate science for the sake of short-
term viewed core business profits.[Ref1][Ref2] Climate change denials and biased or wrong
information about climate by Fox News in the U.S. ,[Ref][Ref][Ref] is seriously misleading public
opinion.Countries like the U.S. put strong emphasis on controversial shale gas exploitation but keep

10. eyes closed for the adverse effect that it brakes the incentive for renewable carbon-poor energy
development and that it has negative impacts on the environment.
A positive outlook, however, is that fusion and hydrogen energy may take over the World primary
energy production during the next century. Replacing nuclear reactors by fast breeder reactors is an
additional option to avoid further CO2 accumulation, an approach advocated even by some climate
activists.[Ref]
 The final message.
In search of explaining their physical environment, modern humans discovered carbon-rich energy, that
allowed them to produce and consume goods at intensities far above what is needed to fulfill basic
needs for existence and prosperity.This is an astonishing paradox as all cultures originally developed
intuitive understanding of limitation, the frailty of existence and the sacredness of natural environments.
In search of prosperity modern civilization has forgotten what intuition had learned.The tools designed
to acquire prosperity have now turned against the designer. However, human beings have a special gift, a
gift that distinguishes them from all other living systems, and that is our special relationship to the laws
of physics, our special ability to create explanations on the basis of these laws and using only energy and
matter.That special gift allows us to discover problems that we caused ourselves and to find the
evidence to explain and resolve those problems. In a World of ever increasing knowledge problems are
inevitable but problems are solvable.[Ref] Our vulnerability is not the failure of getting a solution, but the
failure of getting it in time. If we don’t nurture our gift, we deny our nature and we will disappear.
Therefore, it is crucial to create more knowledge, to make people understand what is known
and to foster a renaissance of human existence.

11.  I end with a few quotes, as I think they are relevant to the origin of the climate crisis and to
encouraging to urgently work at a solution.
Every problem that is interesting is
also soluble.
Inherently insoluble problems are
inherently boring.
David Deutsch
[Ref]
I cannot command winds and weather
Horatio Nelson