After debating it at length with my own self, I could reach my personal consensus. Here are my answers, no proofs, just the envelope in which I feel OK, and I’m taking some risks here. Also, I’m ready to revisit these positions if new evidences arise.
Is temperature going up or not?
The global surface temperature went up over the past 150 years, but stayed flat over the past 16 years.
It started a little bit before the industrial era in coincidence with the end of the Little Ice Age. Interpretation of temperature records is still in debate. Not as many measurement points are available in the Southern hemisphere than in the North. And sea surface temperature has no good historic coverage. Contrary to main-stream beliefs, temperature increase is not a settled issue.
Temperature is not all the story: the sea level began to rise at the beginning of the 19th century, rising by 300 mm over two centuries without good explanation. Regional rainfall anomalies in the past 40 years need also to be better understood.
How much did it go up, and will it go further up?
It went up by about 1°C since temperature records exist, with geographical differences. The variations are larger in temperate latitudes than in tropical or polar zones.
A singular reason would be needed to turn around this trend. But no new evidence has been identified that would now stop the warming. The “pause” observed since the end of last century resembles those that took place in 1880-1910 and 1950-1980, for which no other explanation can be given than on-going oceanic multi-decadal oscillations.
Are greenhouse gases the only cause for the temperature increase?
GHGs play a role, but only partially, approximately 40% of the whole, a primary forcing of 2.6 W m-2. Carbon dioxide is the most important GHG, its contribution to the observed warming is 30%.
To specifically identify this direct cause-effect relationship it is necessary to eliminate all other effects at the beginning and at the end of the observation period. In a subtraction, the error margin on the difference is the sum of individual margins of error: this is no small uncertainty.
The remaining 60%, or a forcing of 2.9 W m-2, are not explained by radiative forcing caused by GHGs.
Is the warming man-made?
Partially. As GHG emissions are directly caused by human industry they have an impact on global and local temperature increases. But, as seen in the previous question, their role shall not be overestimated.
The other part of the observed warming may have other human causes, such as aerosol emissions (e.g. soot, sulphuric acid), or change of landscape (urbanization, agriculture). A quantitative analysis over a long period of time is an impossible task: we have not the data! Obviously, cutting CO2 emission will have no influence on such parameters, and hence on climatic variations.
But as glaciers began to retreat or seas to rise before the full blown industrialization of the 20th century, other natural causes are at play. No validated explanation is given today for the warm roman and medieval periods, or for the end of the little ice age. We may still be in a phase of recovery from the little ice age, with man-induced forcing adding to it. This explanation gap does not disturb me at all. But closing the gap with irrelevant hypotheses is worse than acknowledging ignorance.
Can we trust the results of more or less sophisticated predictive model calculations?
A model can be trusted in what it does calculate, not in what its results may imply. Modellers know the algorithms and their limits, and they take great care in selecting appropriate tuning parameters. With this, they publish model results that are more or less well correlated with observed values. This is mostly honest work of science and of applied mathematics. But so far, the results from almost all of them don’t look that compelling, as seen in the modelling section.
To explain every temperature rise by GHG radiative forcing would imply such a large positive feedback factor that the whole system would be instable. This is a wrong idea, since:
- Published scientific literature, reviewed by IPCC, indicates that it is rather a negative feedback system[1]. An argument of authority, but sustained by the fact that no one proposes outrageously high positive feedback.
- If, despite of all analysis, it would actually be large and positive, then a run-away should have happened by accumulation of forcing over forcing. The fact that the atmosphere tolerated 280 ppm CO2, and tolerates now 400 ppm, is the sole, non-reproductive full scale experiment that we have at hand. Also in earlier geologic era warm periods with high CO2 concentrations have alternated with cold ones. These real-time experiments show homeostasis: the system remained within slightly changed steady-state values.
- Also, responses to volcanic eruptions or to repetitive El Niño events are quite noticeable; but a return to “normal” takes place within a few years. This is an indicator for an inherently stable system with negative feedback.
- You can’t accept homeostasis in the past and reject it for the future when orders of magnitude remain similar.
Forecasting is another story: it involves the selection of an adequate scenario. Are past performances predictors for future evolution? Are long to very long term oscillations (Sun, oceans) well understood? Models don’t explain much.
Having focused almost solely on CO2 as mono-causal warming culprit, the IPCC had to adopt scenarios for further emissions during the twenty first century. These emissions will depend on population growth, economic growth, energy usage ratio in relation to GDP, and on the composition of the energy mix. On top of such hypothetical scenario, global circulation climate models need to be calculated for precise impact assessment. This determinism resembles those of the mathematician Laplace “Une intelligence... Rien ne serait incertain pour elle, et l'avenir comme le passé, seraient présent à ses yeux."[2]. Such hubris was demolished by the relativity theory and quantum physics, but seems to come back into mode.
How bad will be the impact of climate change on living conditions?
Somehow it has been decided that, on balance, the impact of climate change will be high and bad for large portions of the World population. This normalized way of thinking is now pervasive in the press, and among a majority of politicians in the Western World. I have no sympathy for this “pensée unique”.
We have seen in the modelling section that a continuation of human activities at the same growth rate as currently (scenario do nothing) can cause the temperature to rise another 0.4 °C by 2047 and 1.1 °C at the end of the century.
In its latest Assessment Report IPCC writes[3]: “Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for all RCP scenarios except RCP2.6. It is likely to exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5. Warming will continue beyond 2100…”
This is no large difference as compared with my own calculations, but stays in contradiction with IPCC's own estimate of equilibrium climate sensitivity. The difference lies in the interpretation of possible consequences because future impact on living conditions is unknown and can only be described by storytelling.
In the “Summary for policy makers” from IPCC’s Working Group II [4] the most concrete sentence describing the potential impact of climate change is “Impacts of such climate-related extremes include alteration of ecosystems, disruption of food production and water supply, damage to infrastructure and settlements, morbidity and mortality, and consequences for mental health and human well-being. For countries at all levels of development, these impacts are consistent with a significant lack of preparedness for current climate variability in some sectors.”
I really cannot imagine climate change having an impact on mental health! This is morbid wishful thinking of first order.
The sentence cited above is one of the few in this report that are understandable by a normal human being. The summary’s lingo sounds like: “Iterative risk management is a useful framework for decision making in complex situations characterized by large potential consequences, persistent uncertainties, long timeframes, potential for learning, and multiple climatic and non-climatic influences changing over time.” Policymakers are no expert but I can only hope that they interpret this verbiage in the full sense of its idiocy. And if you try to pay attention to these words you find out that they express well hidden banalities.
Despite of this shameful demonstration of United Nation language, I have tried to sort out what stories are deemed important in this report. Besides of repeating at length that temperature is going up and oceans are acidifying the major points are:
- Alteration of ecosystem consisting in melting ice and changing the distribution of species in the ecosphere.
- Worsening food supply where the improvement of food production by higher CO2 concentration may be restricted by lesser access to water and
- Reduced water availability in regions that may become semi-arid or arid.
- Migration of entire populations as the result of the two former points and of other inconveniences such as floods, drought, or storms. This may well be source of armed conflicts.
Somehow in the report a 2 °C threshold (by the end of the 21st century) is instilled above which all consequences of climate change would be “very high”. Policy makers love this: a serious limit to work with, even if nothing is provided to substantiate it. Imagine us at +2.1 °C ? Already dead!
But one should ask: are these potential risks really of such magnitude that we should be worried about them? Is it sufficient to say that thing can go bad to conclude that they will be really bad? And that they are solely related to climate variations?
One evidence today is that no climate victim could yet be identified, with name and address. In fact, by living more and more in cities a great number of people experience already a significant local temperature rise without claiming to suffer from it. From all drawbacks of urbanization, warmer micro-climate is not making the top of the list. And if cities get dangerous we can always construct them in the countryside…
In nature, the slow migration of flora and fauna may oblige fishermen and hunters to adapt, so what? All of this fosters just intelligent adapted human beings, no victims.
Nowadays, dishonest people attribute all meteorological events such as hurricane, floods or tornado, to climate change while there is no evidence to it. Why? In my opinion it is plain herd behaviour: because today we speak of climate change. Fifty years ago it was just weather variations, or earlier, when first texts were being written, just short term prophecies reflecting the climate of the time: seven plenteous years followed by seven years of famine (Genesis 41).
Will adding one degree to the full one gained in 150 years have a negative impact with catastrophic consequences, while we don’t experience any at this time? No honest person knows, only charlatans do.
Are mitigation and corrective action necessary and urgent?
If changes are small, not necessarily bad, and evolve slowly, how should it be necessary to take urgent actions? Why should we do more than just monitoring the situation, wait and, if necessary, adapt? The time scales about which we speak are decades and centenaries, long periods during which constructions can be made, systems can be changed, and lifestyles adapted to other conditions.
When actions are proposed they have to be judged on their merits, asking three question
- Do they serve the set purpose?
- Are they effective?
- Have they undesired side effects?
With the Kyoto protocol and the further pledges made vaguely in Copenhagen, the reduction of CO2 emissions is the major action being underway, at least in a verbal, non-binding context. The Working Group III of IPCC has published its “Summary for Policy Makers” [5] in which it is repeated that warming is man-made and that reducing CO2 emission is of primordial importance, among other proven by … the fact that countries have already undertaken various measures to this effect. In already highly developed countries where growth is now modest, and their economies oriented to services rather than to manufacturing, energy efficiency is improving and CO2 emissions are reduced without big need for activism and intergovernmental agencies. And in those countries to which industrial activities have been shifted and where people aspire to a higher standard of living, curbing CO2 emissions would have no other side effect than a very basic one: it would be the growth killer that nobody wants!
Reducing CO2 emission can contribute to some limitation of the temperature rise. We have seen that by implementing at once a drastic Kyoto-like reduction the containment of CO2 emissions would mitigate the temperature increase by 0.1 °C in 2047 and maybe 0.3 °C at the end of the century as compared to a continuing economic growth without restrictions (hoping that such growth will materialize). For a planetary mobilization involving rapid and drastic changes of the energy supply this expected rescue does not sound very helpful[6]. Tout ça pour ça?
So far and at purpose, I did not make cost-benefit considerations because we know that when something is costing at one place it is making revenues at another one.
The Center for Climate and Energy Solutions[7], not a climate sceptic institution, indicates that electrical power may cost 50% more if carbon capture and storage is added to gas or coal fired power plants. To capture, transport, and store CO2 from various processes may cost between 50 and 100 US $ per tonne. And, let’s not forget, these processes are huge energy consumers by themselves.
[1] IPCC AR5 WG1, p 818, table 9.5
[2] Pierre Simon Laplace, « Essai philosophique sur les probabilités », published in 1814, cited in Wikipedia.
[3] IPCC AR5 WG1, Summary for policy makers, p. 20.
RCP means here “Representative Concentration Pathways” a confusing way to speak about emission scenarios.
[4] IPCC, 2014 AR5, WGII: “Summary for policymakers. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. The Working Group II is in charge of impact assessments.
[5] Interestingly, the summaries for policy makers of WG II and WGIII are already published but the corresponding full reports are still in a draft form. Consensus building is no scientific method, it is haggling at the highest political levels.
[6] To the doctor’s injunctions of stopping smoking, drinking, and fornicating the patient asks if he would live longer. To which the doctor answers: ‘not necessarily but it will feel longer’.