Making smarter climate change policies requires us to acknowledge the limits to our knowledge

LykkeAndersen2By: Lykke E. Andersen*

There is little doubt that human greenhouse gas emissions, mainly arising from the burning of fossil fuels and forests, are warming the planet. The physical properties of CO2 in the atmosphere imply that a doubling of CO2 concentrations from the current 400 parts per million (ppm) to 800 ppm would directly cause an increase in the average global temperature of about 1°C, and with that increase in temperatures we would also experience an increase in global precipitation. That much we know with a high degree of certainty.

Anything beyond that, however, is highly uncertain. While most climate models incorporate positive feedback effects that amplify the initial direct warming effect several times, historical data suggests that there are important negative feedbacks that help stabilize global temperatures. Most importantly, Earth’s temperature has oscillated within a relatively narrow band for hundreds of millions of years despite much higher and much lower CO2 concentrations in the past (see Figures 1 and 2). In addition, during the last couple of decades, global temperatures have not increased nearly as much as suggested by the models with strong positive feedbacks. Thus, we should have only low confidence in our knowledge about feedback effects and temperature increases beyond 1°C.

Figure 1: Global temperature and CO2 concentrations during the last 700 million years


Even if the planet would warm by more than a few degrees, the social and economic impacts of that warming is highly uncertain. The Stern Report found a range of total global impacts by 2100 that correspond to a loss of global GDP between 0 and 8% (See Figure 6.5.d. on page 157 of the Stern Report). Despite hundreds of additional studies since the Stern Report, this wide range of uncertainty still holds. Obviously, there are big differences between countries, with some countries potentially benefitting from climate change, others being largely unaffected, and other suffering severely (1).

The almost certain part of human induced climate change would likely be beneficial for humanity and most other species on Earth, because a slightly warmer, slightly more humid, and CO2 enriched atmosphere means a greener and more fertile planet. It is the uncertain feedback effects that we should be worried about. Even if there is only a small risk of increased CO2 concentrations leading to run-away global warming, pushing the planet outside the stable temperature band within which it has stayed for hundreds of millions of years, that would be a an unacceptable risk, given that this planet is all we have got. You should never gamble with something you can’t afford to lose.

Figure 2: Global temperature during the last 450 thousand years


The high level of uncertainty involved in climate change and its impacts has important implications for climate change policy, and those implications are the focus of this article.

The climate change debate is dominated by two groups of people: Climate change alarmists, who are sure we are overheating the planet; and climate change skeptics, who are sure that the recent temperature increase is mostly due to natural variability.

Both groups are wrong, because there is no way they can be certain that they are right (certainly they can’t both be right) (2). Climate data is incredibly noisy with a lot of natural variability (see Figures 1, 2 and 3), and people tend to see what they want to see in noisy data (3). Even with the recent flattening of global temperatures (see Figure 3), the catastrophic scenario is still possible. However, the beneficial scenario is clearly also possible. Given Figures 1 and 2, I would even add a third possible long run scenario: The risk of returning to ice-age conditions.

Figure 3: Global temperature during the last 100 years


Smart climate change policies need to recognize that these three scenarios are all possible. We need to admit that we just don’t know what the future holds, so we need to prepare ourselves as best we can for all possible scenarios. It would be distinctly stupid to gamble with the only planet we have, so we have to prevent the scenario of catastrophic warming. But it would also be stupid to severely restrict fossil fuel use and keep billions of people in poverty, if it turns out that CO2 actually brings about more benefits in the atmosphere than deep below ground (for example by creating a greener and more fertile planet, pulling people out of poverty, and preventing the inevitable return to ice-age conditions).

Surprisingly, realizing the high level of uncertainty, and admitting that we don’t know for sure whether burning fossil fuels is good or bad for the World, might actually make it easier to formulate and agree on some sensible international climate change policies. This is so because sensible policies are policies that are favorable under any future climate change scenario, and thus should be supported by both climate alarmists and climate skeptics, and anybody in between. The rest of this blog posts discusses a few sensible climate change policies.

It is widely accepted that poor people are much more vulnerable to the adverse effects of climate change than rich people, so a first priority should be to reduce poverty worldwide as quickly as possible in order to reduce the potential adverse effects from the catastrophic warming scenario (as well as poverty in any other scenario). Nobody objects to reducing poverty, so this is a no-brainer, and it should be on top of the climate change negotiation agenda.

Another much less appreciated win-win policy is promoting tree planting, especially in urban areas. Not only do trees absorb CO2, but they also greatly improve the micro-climate around each tree, reducing temperatures, reducing temperature variability, and reducing wind, dust, air and noise pollution. Urban trees greatly enhance property values and promote human health and well-being. Green areas also help absorb excess precipitation, stabilize soils, and thus reduce the risk of flooding and landslides. It is another example of a policy that nobody would object to, so it should also be high on the international agenda.

Closely related to the tree planting policy, is a policy of avoiding chopping down existing trees. Most deforestation is caused by agricultural expansion (for crops, cattle and biofuel crops). This expansion can be limited by: i) increasing agricultural productivity per hectare, ii) reducing the demand for biofuels, and iii) promoting a vegetarian life-style. Here we are clearly running into much more controversial territory. Increased agricultural productivity is best achieved by creating more pest resistant, more nutritious, and more drought tolerant species through genetic modification. But lots of people oppose this idea, mainly because it is new and scary and they don’t understand the science behind it. In this case, science education and good international GMO regulations are necessary. Reducing the demand for biofuels should be easy, as it was artificially created in the first place by not-so-smart climate change policies. A mostly vegetarian lifestyle is an interesting option, as is the promotion of alternative, more environmentally friendly sources of protein, such as certain vegetables and insects.

My last suggestion for clever climate change policies is probably the most controversial, but it is the one that best accommodates all future climate scenarios: Improved physical mobility. Climate change has very different impacts, and some places benefit while others suffer. If people were free to move from inundated coral atolls and drying deserts to places with increased potential, a lot of the costs of climate change could be prevented. In large countries, internal migration could easily accommodate this, but small countries might need increased international migration to find an acceptable place to live.

Even without climate change, there are trillion dollar benefits to be reaped from freer migration (4), so I would put this high on the climate change negotiation agenda as well. While this should be a no-brainer, unfortunately it isn’t yet. But this means that it can potentially be used as a negotiation tool. Poor countries might accept a very ambitious climate change agreement in Paris in December this year, if freer migration were part of that deal.


Dr. Lykke E. Andersen is the Director of the Center for Economic and Environmental Modeling and Analysis (CEEMA) at the Institute of Advanced Development Studies (INESAD), La Paz, Bolivia.


(1) For the case of Bolivia, Andersen & Jemio (2015) “La dinámica del cambio climático en Bolivia” find an average adverse impact of climate change by 2100 of about 16% of GDP. See summary in Spanish here:

(2) See Kathryn Schulz’s TED talk on the importance of realizing that we might be wrong (

(3) See Michael Shermer’s TED talk on the patternism behind self-deception (

(4) See Michael Clemens (2011) “Economics and Emigration: Trillion-Dollar Bills on the Sidewalk?” Center for Global Development.


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