Despite the recent climate agreement in Paris (COP21), where 195 countries adopted the first legally binding treaty to curb climate change, the debate about whether climate change exists or whether it’s the fault of human beings still rages on.

Climate deniers, typically extreme libertarians and anti-government free market advocates, characterise themselves as “underfunded” advocates of “free speech” and “reason”. They characterise the views of most climate scientists and environmental groups, such as the Sierra Club and Greenpeace, as “alarmist” and “left-wing dogma”.

The libertarian sceptics and deniers do no original research, but they constantly criticise the “politicisation” of the Intergovernmental Panel on Climate Change (IPCC). They claim that the evidence of “anthropogenic causation” is extremely weak, and that any climate warming taking place must therefore be of natural origin, or otherwise unexplained.

What can’t be disputed

In the interest of academic rigour, it would be useful to analyse the facts and how the deniers see them. First of all, CO2 levels are undeniably rising. The increase, which many sceptics don’t deny, accelerated after World War II, mainly because of industrialisation of developing countries, increased consumption of electricity, and increased use of private cars and substitution of automotive (and air) transportation for rail-based transport.

But this is the extent of the consensus between climate scientists and deniers.Despite a broad scientific consensus on the importance of CO2 as a driver of climate change, some climate sceptics, and a few outright “deniers” (including the Republican members of the U.S. Congress) still question whether carbon dioxide is actually harmful, on balance. Some argue that carbon dioxide is the “food” for all plants. Plants capture and “fix” that carbon to create the carbohydrate-based food for animals. The natural process (which produces oxygen as a byproduct) is calledphotosynthesis. Without photosynthesis we (and all the other animals) would starve (in fact, we could never have evolved in the first place). Carbon dioxide is the basis of the Earth’s food chain. It is also the source of all the carbon embodied in the fossil fuels our industrial economy depends on.

Not only that, the photosynthesis process is also the source of the oxygen in the air. We humans (and almost all animals) require oxygen to metabolise, and without oxygen we would suffocate. In fact, as the concentration of CO2 in the atmosphere increases, the rate of production of carbon-fixation in organic matter also increases. This is the well-known “carbon fertilisation effect”, and it is exploited commercially in Dutch (and other) greenhouses. It is said that crop production could increase by up to 15 percent in a more carbon-intensive world.

Furthermore (the argument continues), the ozone layer in the stratosphere protects us (and all terrestrial species) from the harmful effects of ultra-violet (UV) radiation. Ozone is a reactive form of oxygen (O3) that is created in the stratosphere by that same UV radiation from the sun. The ozone layer exists because of the oxygen in the atmosphere, which exists because of photosynthesis. Clearly, atmospheric carbon dioxide plays an essential role in the natural world. We could not live without it.

However, most of the climate sceptics and deniers don’t argue on the basis of carbon dioxide and photosynthesis. The majority argue that the science is flawed and the true effect of carbon dioxide concentration in the atmosphere is unproven. There have been vicious attacks on individuals as well as institutions researching climate change. For instance, Lord Christopher Monckton of Brenchley calls it a “climate scam”, adding that the scientific endeavour and policymaking on climate change is “the biggest transfer of wealth in human history from the poor to the rich, from the little guy to the big guy, from the governed to those who profit by governing them.”

But there is no alternative non-anthropogenic theory to explain rising temperatures and therefore melting glaciers, sea level rises and ocean acidification. To invoke “natural variation” is not a theory about causes.

The “pause”

Another recent dispute has focused on the so-called “pause” in climate warming after 1998. If one cherry picks the data, then it seems that there was a slowdown in the rate of temperature increase in recent years.

Figure 1 below shows a graph that was widely circulated in the media (by nay-sayers) allegedly proving that the global temperature did not actually increase for a long period of time. The yellow-shaded area represents the range of 1990 IPCC projections, as contrasted with actual temperature measurements.

Figure 1. IPCC over-prediction from 1990 Report

Part of the discrepancy suggested by this graph turns out to have been based on an erroneous temperature database based on satellite data measurements that had not been correctly “converted” to surface temperatures.

The climate sceptics who stress the discrepancy have made several mistakes. First, they got hold of a (leaked) draft of the fourth IPCC Assessment Report (AR) that was visually misleading because of an erroneous misalignment of observations with trends in the year 1990. A number of nay-sayers published this misleading graph on the web and claimed that it proved that there was no climate warming from 1998 to 2012. The error was corrected in the final AR4, but the naysayers did not retract their claims.

Their next mistake was to confuse the average of all model projections with the actual warming trend. The model projections reflect a wide variety of assumptions about natural variability as well as human activity. But these assumptions show the range of possibilities, not the most likely temperature trajectory.

Third, the nay-sayers who prepared Figure 1 engaged in blatant “cherry-picking” of the start and end dates of the period for which they claim there was no warming. The next graph (Figure 2) shows how different choices of start and end dates for 15-year periods can distort the results. The temperature data are from NASA’s Goddard Institute for Space Studies.

Figure 2. NASA GISS

Note that the long-term trend (1951-2012 black dotted line), shows a consistent temperature increase over the 61-year period, whereas the period 1998-2012 (blue line) shows very little increase (50 percent less than the long-term rate) because of the very warm starting year (a very strong El Nino), while the period 1992-2006 (the red line) shows a 50 percent greater increase, because of the very mild starting year (due to the eruption of the volcano Pinatubo). Note also that 2015-16 (beyond the range of the chart) is another very strong El Nino year that will make the rate of temperature increase look greater again.

Notwithstanding the points made above, it is true that the surface warming trend from 1998 through 2014 was slower than the model predictions from 1990, or even later ones. In other words, there has been a “pause” although not outside the range of recent model projections. This point has been acknowledged in the IPCC AR5 report. The key point is that the models are not (yet) capable of making accurate forecasts of short-term (10-15 year) climate changes. However, the models, tested by backcasting, appear to be reasonably accurate over longer periods.

In the interests of fairness, we can entertain the deniers to an extent on their claim that the IPCC has consistently overestimated its temperature projections. We now know that the original forecasts were considerably off. The forecasts were based on “General Circulation Models” – mathematical models measuring temperature variations in the circulation of the air, ocean and land – were fairly crude in 1990. For instance, there was little information about the temperature of the ocean so scientists relied on data from ships at sea to report on ocean temperatures at particular times in particular places. But since then, the Argo Programme has been launched, which consists of 4,000 bathythermographs (torpedo-shaped probes, floating in the ocean) measuring temperatures as far down as 2,000 meters. Placed in temperate oceans, these probes have drastically improved our coverage of ocean temperatures and therefore the quality of data in the models, improving model forecasting capability significantly.

This is particularly important to building an accurate understanding of the climate, which is a difficult job in the absence of key data. The IPCC has to take into account not just ocean temperatures but air and land temperatures as well. Cloud dynamics and the sea-land and ocean-air interfaces are especially critical.

Despite the IPCC’s acknowledged model weaknesses, the long-term trend is not in doubt. The climate is heating up. The evidence suggests CO2 emissions are the cause and an evidence-based alternative theory is something deniers lack. Another line of debate involves “climate sensitivity”, i.e. by how much the temperature actually rises with CO2 levels. But I will save that for my next piece.

• 
  Antonio FatasPortuguese Council Chaired Professor of European Studies and Professor of Economics

Jean Pisani-Ferry, a professor at the Hertie School of Governance in Berlin, has written a very interesting postabout the need for trusted experts in a democracy. He addresses the criticisms that economic experts have received as a result of the Brexit vote. Quoting from the post:

"Representative democracy is based not only on universal suffrage, but also on reason. Ideally, deliberations and votes result in rational decisions that use the current state of knowledge to deliver policies that advance citizens’ wellbeing."

Very well said. He also mentions the lack of influence of economic experts is not that different from that of other experts (as illustrated by the debates on climate science, GMOs, etc.). I share this view and my guess is that the mistrust of economic experts is simply more visible because of their influence (or lack of) in the political debates that tend to be a lot more present in the media than the debates on scientific issues.

Opinions beat facts

How to enhance the trust in experts? It’s not obvious, according to Pisani-Ferry. What is needed is a combination of discipline among the community of experts, an education system that equips citizens with the tools to distinguish between fact and fiction and the development of better venues for dialogue and informed debate.

Good luck! Unfortunately we are very far from this ideal scenario. Education has reached more citizens than ever before, more so in advanced economies, but we see little impact on reasoned discourse. It might be that the complexity of the issues under debate is at a level which does not allow an informed discussion based on facts and not on ideology. Opinions that are expressed using either the wrong facts or no facts at all are accessible to the public and have an influence that is as large as those who present the facts. And the media does not serve as an adequate filter, maybe because controversy sells or because there is a need to present a 'balanced' view of a debate or simply out of self-interest.

Misinformed media

Here is my example of the day that illustrates this point: the Financial Timespublished two articles on the same day on the merits of quantitative easing. One argued for more QE under the logic that is working and we just need to increase the dosage. The second article presented the view that QE, as well as expansionary fiscal policy, are the wrong tools to use to generate a recovery and that they are likely to lead to a very unhappy ending.

If you read the second article you will notice the use of dubious “facts" and an economic logic that anyone who has ever taken any economics course should realise is badly flawed.

Let me pick one example. The article starts with the figure of 300 percent of GDP for global debt and then it argues that:

"If the average interest rate is 2 percent, then a 300 percent debt-to-GDP ratio means that the economy needs to grow at a nominal rate of 6 percent to cover interest."

This is just wrong on so many counts:

• The increase in debt in the world is matched by an increase in assets.
• The interest rate paid by borrowers goes to lenders. So the world (or a given country) does not need to find income to pay for this interest, this is a transfer from borrowers to lenders.
• Borrowers need to pay interest but if debt is coming from a mortgage to buy a house, rent is no longer paid. Looking at interest payments alone (or at liabilities without taking into account assets) is just wrong.
• The 300 percent number cannot be associated to a country or a government, most debt is internal. No country has an external debt that is anywhere close to that level. Same is true for governments (with the exception of Japan which is not far off, but, once again, most of this debt is internal – so the interest that the government of Japan has to pay goes to the Japanese citizens who happen to be the taxpayers).
• Even if you had a government that had 300 percent of debt, the calculation above is simply wrong. If interest rates are 2 percent, you need to grow at 2 percent (not 6 percent) to ensure that the debt-to-GDP ratio stays constant (as long as your additional borrowing or saving is zero, of course). This is something that is taught in a principles of economics course. The authors are confusing the value of interest payments and the required growth to make that level of debt sustainable.

The rest of the article contains many other mistakes. It is embarrassing that the Financial Times is willing to publish such a low quality article.

Will this article influence anyone's view on the debate on monetary policy? I do not know but what I know is that the pessimistic view presented in the article on the role that monetary and fiscal policy is popular enough that is still influencing both the debate around and also the outcome of current economic policies.

We are very far from having informed and factual debates about the economic (and scientific) issues that shape economic and social outcomes. As an economist, I continue to do my best by sharing my views and analysis with a wide audience through blog posts like this one but it is depressing to see how those that rely on flawed analysis often manage to reach the public through the validation of the most respected media.