Is the planet getting warmer?

There have been 1000s of academic papers written on climate change as a whole - about 15,000 a year over the last 5 years according to a simple search for “climate change” on Semantic Scholar [1]. Lest we think that is a sign of environmental scientists on a boondoggle, compare it with the roughly 85,000 papers a year for a similar simple search for “breast cancer”, and of course it is that research over the years that has led to such progress being made with this disease, with 100’s of thousands of lives saved.

The scientific consensus on both the fact of global warming, and human activities being the primary cause, is clear. Numerous studies have been done summarizing the huge body of research - for example a study in 2012 by Jim Powell (a member of the National Science Board for 12 years, appointed first by President Reagan and then by President George H. W. Bush) found that from 13,950 peer reviewed climate articles, only 24 (0.17%) rejected human-caused global warming! [2]

Not really much that I can add to that, except maybe some guidance on where to get information, and how to interpret. Again thinking of other areas of scientific research, if you were unfortunate enough to be diagnosed with breast cancer, you would be foolish to start your treatment plan by diving into the 100,000+ papers, or by plucking information from sites on the internet of dubious trustworthiness and scientific basis, rather than at least first talking to some respected doctors. What’s the climate equivalent of that trusted doc?

Firstly, there’s the USGCRP (United States Global Change Research Program). This program was started by the George H.W. Bush administration way back in 1990, with a mandate to “assist the nation and the world to understand, assess, predict, and respond to human-induced and natural processes of global change." It makes sense to establish such a program, and I’ve seen similar through my career in the private sector - when you see a potential threat or problem, you assign a group of people to go research it, understand it, and recommend what action if any needs to be taken. Thirteen different US agencies are involved, and the program includes:

• Periodically releasing a National Climate Assessment (NCA) report, that details the current understanding of what is happening, why, and the impact on the US. Led by NOAA, but using 300 scientists, half of whom are outside the government. Reasonable to say that this represents the official position of the US government on the science of climate change.
• The Federal Advisory Committee, responsible for helping state and national policymakers incorporate the government climate analysis contained in these NCA reports into long term planning.

The most recent assessment report (NCA4) was released in two parts:

• Vol 1 of NCA4 (“Climate Science Special Report" CSSR) was released in October 2017. This section of the report covers the state of climate change science - the “What’s happening, why, and future projections”
• Vol 2 of NCA4 (“Impacts, Risks, and Adaptation in the United States") was released in Nov 2018. This section of the report covers the impact on the US - more the “What does this mean, and should I care?”

Both parts are very readable (albeit worrying), and contain high level overall summaries, and an easy way to just read the key findings of each section. The full reports are Vol I and Vol II, with the executive summaries at Vol 1 (summary) and Vol II (summary) (just scroll down).

Given the breadth of these reports, we will encounter them again in other sections below. But what do they have to say specifically on the question of warming? Well, given that your tax dollars paid for them, and your kids/grandkids futures depend heavily on our response to them, I suggest you go read the summaries/key findings yourself! But, some highlights from the executive summaries:

• The global, long-term, and unambiguous warming trend has continued during recent years.
• Global (sea and land) annual average temperature has increased by more than 1.2°F (0.65°C) for the period 1986–2016 relative to 1901–1960. This means an increase over the entire period from 1901–2016 of 1.8°F (1.0°C) i.e. the change from “preindustrial times”, which is often used as the benchmark in papers and government reports.
• Sixteen of the warmest years on record for the globe occurred in the last 17 years.
• Longer-term climate records over past centuries and millennia indicate that average temperatures in recent decades over much of the world have been much higher, and have risen faster during this time period than at any time in the past 1,700 years or more.

So that’s the position of the US. What’s the opinion of other countries? Here it makes sense to look first to the IPCC (Intergovernmental Panel on Climate Change) which is the United Nations body for assessing the science related to climate change i.e. the UN equivalent of the USGCRP in the US. Created in 1988, the IPCC has 195 member countries, including of course the US. Very like it’s US counterpart, the IPCC prepares comprehensive Assessment Reports about the state of scientific, technical and socio-economic knowledge on climate change, its impacts and future risks, and options for reducing the rate at which climate change is taking place. The IPCC does not itself conduct research, but instead commissions and scopes reports, selecting groups of experts as authors, and as reviewers. Again, this is very similar to my experiences in business, where we would hire an independent unbiased expert to write a report on, say, the state of the market, as expert input on which to base decisions.

There have been a number of Assessment Reports (ARs) released, each in multiple sections covering the science, mitigation, and impacts of climate change. The most recent was AR5 in 2014, with AR6 in progress, and due to be published April 2021 to June 2022. This report will be the first to assess the Paris Agreement, and, I predict, will make more thoroughly depressing and worrying reading given current progress. All the reports can be seen on the IPCC site The (now dated) 2014 AR5 is in agreement with the US equivalent on the question of the planet warming - from the introduction:

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen.

More interestingly, the IPCC has commissioned & released periodical ‘special reports’ - we will meet some of them later.

I should say, a lot of the charts and diagrams in these reports aren’t the best ones around for conveying what’s happening. An example of a better one is below : it shows the monthly temperatures from 1850 to 2016 in a spiral, with the color of the line changing from purple (1850) through blue and green to yellow (2016). It helps highlight not only the warming as the spirals move out, but the acceleration of the warming as the gap between successively spirals widen - watch the animation of this visual below.

Ok, so that’s a summary of two government bodies from the US and the UN, involving 100s of scientists. But as someone who has worked in data analysis for years, I can’t read anything like this without jumping in to take a look at the data myself! I certainly don’t think that a quick bit of amateurish analysis of temperature data is going to add much weight to the conclusions of all those scientists, but exploring it a little helps understand the nature of the analysis being done, and particularly how parties with vested interests can confuse, obfuscate and mislead. So I went and grabbed monthly average temperature data for Miami Airport (1948-2019), as collected and published by NOAA. Plotting a simple graph of average temperature for the year, by year, gives us the following (note the table doesn’t show all the values on the chart):

This sort of graph is common in climate science, and other domains. Certainly there are huge variations from year to year, and of course if we looked at monthly, or even daily or hourly average temperatures, we would see even more detailed variations. But we are trying to determine the overall trend. What we definitely do not do is pick two points, and compare them. For example:

Both are true statements based on the data - both are useless at best, highly misleading at worse (yet we see policymakers do basically exactly this). Anyone who does this is almost certainly trying to prove a point with some hidden agenda. Even more ridiculous than choosing selected years, is drawing conclusions from selected months or even days - “last July was the hottest on record” , “last Tuesday’s -5 °F was a record low”.

Of course, determining trends among such chaotic data is what scientists do, whether that data is showing temperature, or cancer rates, or the FTSE. One approach is to “smooth” the data, for each year calculating the rolling average over the previous 5 or 10 years. That makes sense - if someone asks you what the climate is like where you live, you probably think back over the last few years before you answer.

So if we do that, then plot the graph of the smoothed temperate by year, what we get is:

The graph now allows us to more easily see the overall trend among the chaotic year-to-year variations. Statistics give us other tools as well of course. One example is calculating the “trend line”. Assuming that there is a straight line showing the temperature by year - which is the line that best fits that data we have? The result is the dotted line below, clearly showing the upward trend.

The important thing about such techniques is that they have no internal biase. There is a strict mathematical definition of “best fit”. They don’t care whether the data is temperature, house prices, or your golf score. They certainly don’t care whether you are a Democrat or a Republican ( I should say that the use of trend lines like this is unusual for climate data. The more normal approach is to compare averages for one period to averages for another. The principle of impartiality is the same).

The other value in exploring the data ourselves is to gain an appreciation of some of the challenges of doing this kind of analysis. Some examples are below - the first few examples are common to almost all such analysis over large amounts of data, others are more specific to climate changes research specifically.

• Data is often incomplete. Even in the NOAA data, there were often years without a temperature for every month, leaving the possible danger of comparing a year with data for only the winter with another year covering only the summer. How are such omissions addressed?
• It’s necessary to look at reasonable time periods. If examining overall trends, it is meaningless to look at short time periods, meaning multiple decades in the case of climate change.
• The data to be included must be carefully selected to be representative. For example, which of the 100s of weather stations should be included, especially is this covering both land and sea, and how to account for the fact that urban areas tend to be warmer than rural areas, yet most weather stations are in urban areas?
• There have been numerous changes over the years - weather stations have moved, and the type of thermometer used has changed, as has the time of day when the temperature was recorded. Such changes must be accounted for.

The overall effect is that no useful scientific analysis is just using raw data without some adjustments. Especially as some analysis is looking further back into earth’s history, before the first records began, estimating temperatures based on other evidence. The important point of this is:

• A lot of dispute/discussion between different scientists will be on the detail of such adjustments made in any particular piece of research - the consensus remains that the Earth is warming.
• Extreme care has to be taken in reading analysis from sources that do not provide information on what they have done, and that is not subject to scientific review. As shown above, it is extremely easy to make true statements that are so misleading as to be dangerous lies.

Finally, let’s look at an independent, non-government, source. There are obviously many research bodies I could choose from. I chose Berkeley Earth because:

• It was established specifically to look at some criticism by climate change ‘skeptics’, as to over-estimation of warming from previous studies.
• It is independently operated, funded primarily by unrestricted educational grants, and has received funding from both sides e.g. the Koch Brothers, notorious for funding research aimed at undermining the scientific consensus, and Energy Foundation (who promote alternative energy).
• It appears both transparent as to its methods and data (allowing its conclusions to be understood and verified), and given it’s criticisms of other scientific studies and some of the other papers published, appears impartial. For example, they have published papers on natural gas and fracking (hardly the darling of environmentalists) [3] [4], arguing for the environment benefits inherent in the move from coal to natural gas that fracking has helped precipitate.
• I have seen Berkeley Earth referenced as a “source of truth” by some climate change deniers online.

Brief descriptions of all their results can be seen here.

Their initial study was looking at issues raised by skeptics of other studies, on possible biases from urban heating (where urban areas tend to be warmer), data selection (choices made as to which stations are to be included), poor quality of station data, and the data adjustments done during the analysis. Their conclusion:

The average temperature of the Earth’s land has risen by 1.5 °C (2.7 °F) over the past 250 years (from 1770, about the time of the James Watt steam engine), of which 0.9 °C (1.6 °F) over the past 50 years - this is consistent with other studies

This is in line with other studies, showing that the issues raised by skeptics did not bias the results

Note that this study only looked at land temperature, hence shows a larger increase than those above of the US government and IPCC, that covered land and sea (with sea warming slower than land).

The website also includes:

• A paper [4] published back in 2013 on the claims being made at the time by skeptics that global warming had stopped. And of course, temperatures in the years since then have shown how wrong those skeptics were, and how correct the Berkeley Earth analysis was, adding further credibility to their current conclusions.
• A detailed discussion of adjustments needed [5], what adjustments were made as compared to other studies, including the statement “I can say with certainty that there is no grand conspiracy to artificially warm the earth”.
• Information on temperature increases by region (country, state, or city - go look for your hometown here)
• Criticisms of other studies/scientists [6]

Summary

In summary: The global scientific consensus of government and independent research is that overall the Earth has been getting warmer over the last 120 years. I feel it is fair to conclude that anyone stating that they do not believe that either:

• does not apply science to their beliefs at all, or ;
• is prone to believe in conspiracy theories that would need to encompass thousands of scientists worldwide, or (more likely);
• has a strong vested interest in no action being taken, with their calculation being that the benefits they personally gain will be greater than the damage they and their children personally face (factoring in the protection they believe is offered from their wealth).