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What Bill Nye could have answered if he had a clue

Willis Eschenbach was provoked by the following 9-minute discussion between Bill Nye and Tucker Carlson, a Fox News host:

About one-half of the TRF readers live outside the U.S. and some of those may be unaware of the existence of Bill Nye. He's an American "socialite" (an occupation that makes many people rich enough in the U.S.), basically a male counterpart of Kim Kardashian. Whenever one of them oils his or her butt, the tabloid media don't write about anything else for a week.

Kim Kardashian's and Bill Nye's incomes depend on being seen. In particular, Bill Nye was a contestant in Dancing With the Stars and owes about 50% of his income to his bow tie which he has to wear at all times. If a tragedy occurred and he lost it (I mean the bow tie, he has lost the plot some time ago), he would be in big trouble. Most of the remaining 50% is owed to Nye's successful theft of the show of Professor Proton.

Many people still remember him mainly as an actor starring as the "science guy" in an educational and entertaining show for children aired between 1993 and 1998. The kids who watched it may have been 10 in average and now they're about 30. As the interview at the top and many other activities of Bill Nye indicate, he must believe that most of his viewers from the 1990s still can't distinguish Hollywood from reality and are ready to buy the idea that he is an actual scientist, not just an actor who played one.

Sadly for him, interviews such as the one at the top could only persuade the 30-year-old children who were really, really left behind and are retarded by some 25 years. When the discussion about the climate began, Bill Nye proudly embraced his one-year-old quote about some terrible death for the climate deniers.

When Carlson indicated that he wanted the discussion to be a little bit more high-brow, Bill Nye protested and argued that the most important question that scientists are trying to answer in 2017 is the question what kind of a delusion or cognitive dissonance operates inside the climate deniers' brains. He was trying to convince Bernie Sanders just hours earlier that this question is what all the top science is about in 2017. ;-)

Well, 30-year-old children who believe that actual scientists are really trying to answer this question or similar questions were really, really, really left behind and Tucker Carlson apparently wasn't one of those. Because Bill Nye repeatedly said that it's been settled that the sky is falling, Carlson wanted to know at least some detail about what has actually been settled. He asked the question or questions that are the basic ones for anybody who tries to approach the debate at least somewhat seriously:

To what degree the mankind has helped the climate to change and what the climate would look like in 2017 if the human industrial civilization weren't around?
This is an obvious and obviously good and legitimate question or, I would say, a "sketch of a question". Sadly, Nye has failed to give anything that would resemble an answer. The word "degree" was used by Carlson and is somewhat vague. It makes it clear that Carlson wants to know at least something quantitative because it's clear that the humans could have affected something and somewhat. But the word "degree" is also sufficiently non-standard or vague so that we don't really know which exact quantity we should quantify while answering the question. We may still try to answer roughly "this" question and it may be useful.

At various points, Nye said that the rate of climate change was made insane by the humans, that a similar amount of climate change would otherwise take tens of thousands or millions of years – he seemed rather confused about the difference between these numbers and at one moment, he was basically saying that dinosaurs lived tens of thousands of years ago ;-) although he mostly corrected himself later – and that humans were responsible for "100 percent" of climate change. All these statements are absolutely preposterous from the scientific viewpoint but one simple answer that Bill Nye gave,
Without humans, the climate now would be about the same as the actual climate was in 1750
is a proposition that I would actually agree with. Many skeptics don't agree. They say that Bill Nye cherry-picked a cold moment – 1750 was in the Little Ice Age and was therefore cooler than the present for natural reasons.

I think that these statements by the skeptics are silly. First, the year 1750 was probably used because the industrial revolution began roughly at that time. I am using the very same number as the "beginning of big industrial effects", too, which is why I am not going to criticize Nye for having done the same.

Second, some people seem to generously think that everything between 1650 and 1850 was the "Little Ice Age". I think it's highly inaccurate. The climate was still changing rather intensely between 1650 and 1850, too: it's always changing and 200 years is a rather long time. Some data indicate that the cold periods were around 1650, 1770, and 1850. At some places, the 1820s seemed very cold, and so on.

But you may look at your favorite places to have an idea what the temperature in 1750 looked like. The Central England Temperature indicates that 1750 could have been one Celsius degree cooler than the present but some years in the previous two decades, 1730s and 1740s, were significantly warmer and it's rather likely that at least some of these years were actually warmer than some recent years.

Alternatively, look at the Prague's Klementinum record collected in the Jesuit library near the Charles Bridge. The first century after the beginning in 1770 saw "mostly cooling" and it was followed by "mostly warming". The record doesn't quite go back to 1750 but it seems totally plausible – especially if you extrapolate the graph in the most natural way (and if you realize that other datasets indicate that 1770 was actually cooler than the nearby decades) – that the temperature in Prague of 1750 could have been virtually indistinguishable from the temperature in a recent year. (And some of the warming in downtown Prague could have been due to the increasing urbanization.)

You may also compare the picture of the Karlštejn Castle in 1750 and Karlštejn now. You can see that the castle has gotten a new, darker roof to gain its "modern form". But there's not much detectable difference in the climate. Bill Nye speculated that some French winemakers were buying more Northern fields in France that they would be buying if humans weren't around. ;-) Maybe, maybe not, maybe some of this drift was contributed by CO2 but even if it has been, the expansion of the vineyards in the Northern direction is surely not "more dangerous" than a symmetric or Southern expansion of these fields, is it? Even if the difference of temperatures were about 1 °C, it would be extremely hard to actually detect it. You would need to average the temperature over a big portion of the globe and over days, seasons, and several years to get rid of the noise that would otherwise overshadow the 1 °C difference.

So again:
I basically agree that science naturally predicts that without the human influences, the temperature today would be predicted to be equal to the temperature in 1750, plus minus some natural noise. And another part of the answer is that within the centennial natural noise, the temperatures in 1750 and 2017 are basically the same!
Especially when you compare the recent temperatures with those in 1750, you can see that the mankind hasn't made any easily detectable difference for the climate. When it comes to the climate, people are still either irrelevant or they are just beginning to be "comparable players" to natural drivers that have always existed. These two possibilities sound qualitatively the same but there's obviously a "continuum" – you probably can't sharply say which of these statements is more accurate.

At any rate, there doesn't exist any reason for any concern when it comes to the human influence on the climate. Every competent and honest scientist knows that.

Otherwise, the global mean temperature has been evolving since the birth of the Sun, Earth, and Solar System over 4.5 billion years ago. At the very beginning, the solar radiation is believed to have been a bit weaker, because of the evolution of our star as retrodicted by the nuclear physics-based models. That should have implied that the Earth was cooler than today, by many dozens of degrees. The water should have been frozen. But there is geological evidence that there was liquid water on Earth from the beginning. This apparent contradiction is known as the faint young Sun paradox. It hasn't been settled what is the "neglected early warming influence" that solves the paradox but there are many candidates for a solution – a different composition of the early atmosphere perhaps including lots of greenhouse gases, radiogenic heat, tidal heating, volcanic activity, and others.

Temperatures were always changing and this graph depicts the situation of the recent 600 million years. You see that the graph seems to say that the global mean temperature was always between 10 °C and 25 °C. It's a rather wide interval but it's not terribly wide. Fluctuations comparable to several degrees have always existed – even the body temperature may fluctuate by a degree, especially if you're ill – but it seems that the fluctuations were never "many dozens of Celsius degrees". Some mechanisms have stabilized the Earth's temperature – protected it against these "more qualitative changes" – at all times and all time scales.

The graph is a bit exaggerated – it really indicates that the Earth wanted to be near the levels 10 °C and 25 °C for a big part of the time and it was "almost dogmatically" kept within this interval. I don't believe it can really be true so the graph is idealized. But I do think that the graph reflects some of the main warm and cold eras according to the scientific reconstruction we may have – and gives one a good idea about the magnitude of the fluctuations.

Note that in hundreds of millions of years, the positions of continents are moving so the Antarctica wasn't near the South Pole etc. All these things influence the continental as well as global mean temperature.

I must also mention that the graph above looks constant for millions of years, it is rather smooth. You shouldn't interpret this fact as the statement that the temperature was really constant for millions of years, within a degree. The graph above is a result of some smoothing and averaging. So to imagine what was really happening with the temperature, you should imagine a superposition of the long-term graph above (that only correctly captures some very low-frequency variations) with some faster fluctuations that appear e.g. at tens or hundreds of thousands of years, with some shorter cycles, quasi-cycles, and other changes, and obviously with the day-night and seasonal cycles, too.

All these faster cycles have always existed.

In the recent 450,000 years, the ice core taken from the Antarctica shows that the temperature fluctuated in a window whose width is comparable to 10 °C. That's enough to change the climate substantially. So we had the ice ages and interglacials alternating with each other "quasi-periodically", with the "quasi-periods" in between tens and thousands of hundreds of years. Note that these glaciation cycles didn't always exist. In the somewhat recent era, periodic continental ice sheets only started to be created some 2.6 million years ago when Quaternary began. (The previous sentence is a tautology that follows from the definition of the Quaternary and especially of its beginning.) In the previous 20 million years, the Neogene, there weren't ever big continental ice sheets.

It's known that the glaciation cycles in Quaternary were driven by astronomical cycles, the Milankovič cycles. Due to the aperiodic influence of other planets on the Earth etc., the eccentricity of the elliptical orbit (how squeezed or thin or "far from a circle" it is) and the tilt of the Earth's axis (which is 23.437° today but it wasn't always like that – the tilt is decreasing these days, by a degree per 10,000 years or so) are somewhat variable. Both quantities influence the "magnitude of the temperature difference between winter and summer" and therefore the rate at which the continental ice sheets grow (or melt) on Earth – the Arctic circle around June is the key combination of place and season – and the volume of the continental ice sheets affects the temperature on whole Earth for thousands of years.

On the other hand, it's totally plausible that some hundreds of millions or a few billion years ago, there were sometimes continental ice sheets as well, and they could have alternated just like they did in the recent 2.6 million years. There exists some evidence that the Earth could have been completely frozen at least once, e.g. as the snowball Earth 650 million years ago.

To have a realistic idea what the climate looked like 400 million years ago, you should combine the rough smooth graph from the recent 600 million years ago with faster oscillations similar to the Vostok graph from the recent 450,000 years ago, with the centennial flukes, seasonal oscillations, and day-night oscillations etc. The daily, seasonal, but even some other (a bit slower) cycles were basically and qualitatively the same as we know them from the 21st century but they were oscillating around a different baseline and the baseline is always captured in the graphs describing the longer timescales.

So throughout the billions and millions of years, the temperature of Earth was always changing although the sufficiently averaged temperature changes never seemed to exceed some 30 °C, at least not by much. At shorter time scales around 1 million years, the temperatures tended to be within a window that is at most 10 °C wide.

But once you want to be more ambitious and accurate and you're not satisfied just with the rough knowledge of the ice ages when the temperature decreases by 8 °C relatively to the warm interglacials, things become complicated because the number of effects that have the ability to change the global mean temperature by 0.5 °C or so is very, very large. The following effects may be "named" that were capable of producing a 0.5 °C temperature change in the recent century:
  • The greenhouse effect from CO2: one doubling of the CO2 concentration produces some 1.2 °C of warming without feedbacks and the CO2 emissions have already done the work of "one-half of the doubling", so they could have added 0.5 °C since 1750. I placed this effect at the beginning because it's the root of the "debate" and it's also the effect with the most predictable, positive sign – the man-made emissions have always contributed to warming and never to cooling. The following entries are more ambiguous or fluctuating when it comes to the sign, and some of them are more temporary.
  • Urban heat islands (UHI), another man-made effect at the beginning: a typical new city is warmer by some 0.5 °C in average than the area before the buildings, asphalt roads, and other things are built there. These increases last as long as the cities, they only affect a few percent of the area of the globe, but a very high percentage of the humans because they tend to live in the cities, and a large percentage of weather stations because many of them are in the inhabited places or cities, too. One must be careful about this effect while measuring and interpreting temperatures and one must be careful about all these effects while trying to explain the data.
  • El Niño and La Niña episodes: reasonably strong episodes of the weather patterns in the equatorial Pacific – which are quasi-periodically alternating every two years or so – are able to cool or warm the global mean temperature roughly by 0.5 °C from a baseline. It's somewhat unknown whether these contributions are "being forgotten" or "they are largely accumulating". It's possible but not certain that a statistical uptick of the number of El Niños from the late 1970s has significantly contributed to the apparent warming in the recent 40 years, for example.
  • Pacific Decadal Oscillation (PDO) and other slower ocean cycles: when one looks at the intervals of length around 80 years, it seems that some slower ocean cycles affect the climate (and weather). The positive and negative phases of PDO (which like to last for 30 years or so) are capable of adding or subtracting 0.5 °C as well, and this effect may last for decades or longer. These slower ocean cycles aren't necessarily independent from the faster ones. It's plausible that the warm phase of PDO makes El Niños more likely, and so on.
  • Volcano eruptions: a big enough volcano eruption emits some dust which reflects the solar radiation and may cool the Earth by 0.5 °C, sometimes for years. Mt Etna erupted just when I was writing this paragraph: live. If you happened to get many fewer eruptions than normally, this deficit could warm the Earth.
  • Cosmoclimatologically driven oscillations in cloud cover: variations of the cosmic rays and the solar activity that helps to shield them (reliably or not so reliably) may affect cloud cover and these changes of the cloud cover may arguably produce 0.5 °C in either direction although all the numbers remain disputed.
  • ...
  • Aside from all the things that may be "named", there are also influences that can't be this easily attributed and named, but they still exist. In particular, "the weather" always exists and is random – and it is often autocorrelated which means that you simply can't rely on the assumption that the weather over a 30-year period perfectly "averages out" to something that is predictable. I don't believe it's the case. Just like you may have a bad weather for weeks, "some kind of a bad weather" or a pattern may affect a region for decades or centuries. Some of the "modes" have been named and mentioned but others haven't or can't. My more ambitious point is that there is really no timescale above which the weather becomes irrelevant – weather is a scale-invariant phenomenon. Just like the weather often doesn't average out for a month (and your whole vacation sucks), it doesn't average out over a decade. For example, a system of winds or some circulation around Antarctica may "sit there" for a century and shield the Antarctica from the warming of the (almost whole) rest of the globe, but this circulation may disappear a century later (or any other time scale later). In order to make these qualitative observations useful, one must be quantitative and study "how large is the statistical leftover that doesn't average out" for various time intervals and other parameters of the averaging.
The broader point is that once you are trying to explain or predict the Earth's global mean temperature with the accuracy that is finer than 0.5 °C, you face the task of correctly quantifying the influences of very many effects from different parts of physical and Earth sciences. None of them is known too accurately and many of them are known extremely inaccurately which means that the amount of ignorance is very high for your purpose. It's at least a sociological fact that no one has been able to tame or quantify all these effects accurately enough so that others would consider his answer as the "obviously final one". So the strength of the greenhouse effect caused by gases different than water vapor (the main greenhouse gas which adds roughly 20 °C to the temperature on Earth) is at most as strong as many other effects we know – having contributed some 0.5 °C to the temperature over a century (or since my and Nye's year 1750).

So the answer to Carlson's question about "the degree" is that at timescales comparable to decades or a century, the man-made CO2 is responsible for a percentage of the global mean temperature change that is comparable to 50% but the precise number depends on the exact interval and the precise question asked about the interval – and the precise percentage isn't known to science, anyway. But it's known with near certainty that the percentage is neither above 95% nor below 5%. It is irrational to single out the greenhouse effect. The precise relative importance of the greenhouse effect and e.g. ocean cycles or volcanoes or variations in solar activity etc. isn't known. But it is known that it is impossible to describe the climate well while only taking one of these effects into account.

The carbon dioxide simply isn't the climate control knob, as Tom Nelson likes to repeat 30 times a day. ;-) At the same moment, we know that the volcanoes and other separately considered effects, while important for the sub-degree accuracy, aren't the universal and unique climate control knob, either, and the same may be said about (all or almost all) the other effects I have enumerated.

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