IPCC First Assessment - What we can learn from a 30 year old report

-

The Intergovernmental Panel on Climate Change (IPCC) was established in 1988. It produced its First Assessment Report (FAR) in 1990. 3 decades later, much remains to be learnt from this superannuated report.

To remind the reader, in the last 30 years we got computers, mobile phones, internet, smartphones and smart TVs. India saw 6 different Prime Ministers and 7 different Presidents in this time span. There were 8 ICC World Cups; India defeated Sri Lanka to win one of these. 1990 was 4 years before Andaz Apna Apna; in fact, it was the year when Sri Devi got an award for Chaalbaaz. Titanic was still 7 years away; The Matrix, 9. You may also look towards your own life to remember what the last 30 years meant, but I believe the point is quite clear -- 1990 was a long, long time ago.

In this 3-part series (one for each Working Group), I take a very cursory look at the First Assessment Report (FAR). The aim is not to delve into technical details, for which I hope you will explore the original reports available on the IPCC website. The aim, instead, is to try to position ourselves in 1990, understand where we stood back then and hence, try to understand how far we've come.

Working Group I (Science)

Back in 1990, the IPCC informed the governments all over the world about some gases that were enhancing the natural greenhouse effect.


We have now added a few gases to this list (notably, Ozone -- whose effect the FAR did mention but could not quantify -- and Sulfur Hexafluoride), but these 4 gases remain among top concerns even today. Thus, the main culprits for climate change were known 30 years ago.

Feedbacks

It was also pointed out that global warming would increase the concentration of water vapour (also a greenhouse gas) in the atmosphere. Thus, the concept of feedbacks was introduced. To put it simply, a feedback is something that both affects and is affected by a process. In this case, it's a positive feedback -- warming leads to more water vapour, and more water vapour leads to even more warming. It was pointed out that climate models which are used to make "predictions" about the future do not take into account all known feedbacks. (This is true today as well. As our understanding of feedbacks grows, we also face fresh challenges for their incorporation into climate models. Climate models are, like most things being researched, a work in progress.)

This makes the whole situation more complicated and worrying. The FAR stated, "It appears that, as climate warms, these feedbacks will lead to an overall increase, rather than decrease, in natural greenhouse gas abundances. For this reason, climate change is likely to be greater than the estimates we have given." Thus, if climate modelling is to be taken with a pinch of salt, it is far wiser to take results as under-estimates rather than over-estimates.

The predictions

The FAR gave predictions under four modelling scenarios: A - D where A was also called "Business-as-usual". We can now compare what they predicted with what has happened since. Today, the CO2 concentration stands at ~412 ppm. This lies within the bracket estimated  by the IPCC.


The temperature profiles turned out to be over-estimates. Today, the global mean temperature has risen around 1.2 ℃, which falls below the FAR's estimate for Scenario D (their most optimistic scenario) of almost 1.5 ℃. A happy mis-prediction, no doubt! What led to this over-estimation, how it improved climate modelling and how the improvements were incorporated in further IPCC reports would likely fill many blog posts.

A clear admission of uncertainties

The report clearly distinguished between what was known with certainty and what was estimated with what degree of confidence. The FAR stated, "The size of this warming is broadly consistent with predictions of climate models, but it is also of the same magnitude as natural climate variability. .. The unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more." Thus, the question -- "Man or nature?" -- was not answered back then. Perhaps this didn't make for a very strong cause for climate action back in 1990, but it adhered to scientific values.  In the section "How much confidence do we have in our predictions?", the authors write, "..climate models are only as good as our understanding of the processes which they describe, and this is far from perfect. .. Nevertheless, for reasons given in the box overleaf, we have substantial confidence that models can predict at least the broad scale features of climate change."

It vexes me when climate deniers / sceptics try to undermine confidence in climate models by using the argument "climate models aren't perfect". First, nothing is perfect. As Gavin Schmidt puts it, if we had observations of the future, we would obviously prefer those! We use climate models because observations of the future are not available at this time. Thus, to put it simply, climate models are not perfect but they are (A) good enough and (B) the best we've got. But secondly, using this argument makes it seem as if scientists are claiming the models are perfect! That is quite far from the truth.

Another noteworthy admission was related to weather variability. The report says, "With the possible exception of an increase in the number of intense showers there is no clear evidence that weather variability will change in the future." Note the statement, the FAR states that there is no clear evidence -- thus, it could not comment on this aspect. Simply put, they did not know.

Yes, they knew about the Sun!

One sticky climate myth that seems to do the rounds frequently (likely because of its alluring simplicity) is "It's not us, it's the Sun". On behalf of climate scientists around the world, I can assure all readers - Yes, we know about the Sun! 

Speaking of natural factors which affect climate, the FAR stated:


Conclusion

So back in 1990, we knew that carbon dioxide, methane and some other gases were trapping heat in the Earth's atmosphere. We knew this would warm the Earth, but we had only a vague idea how much. We knew there was a lot we didn't know and would require research. One can also understand if this report did not lead to any significant policy measures right away. After all, there were considerable uncertainties in what could happen. Also, we weren't sure if this was our doing (and hence, could be undone by us).

And even if we had to begin, where would we start? Did we have a clear idea? The FAR was suggestive, "Since the industrial revolution the combustion of fossil fuels and deforestation have led to an increase of 26% in carbon dioxide concentration in the atmosphere. We know the magnitude of the present day fossil-fuel source, but the input from deforestation cannot be estimated accurately. .. Emissions of chlorofluorocarbons used as aerosol propellants, solvents, refrigerants and foam blowing agents, are also well known, they were not present in the atmosphere before their invention in the 1930s."

Fast-forward to 2020. The IPCC has since released 4 more Assessment Reports. The diagnosis of climate change and the role of anthropogenic activities are clear. The prominent role of fossil fuels is clear. The Montreal Protocol has been implemented successfully, the CFCs are being regulated -- showing global coordination can work! The impacts have started showing up in the form of hotter seasons, extreme weather events and forest fires. Climate models have advanced considerably, predictions have improved, thus bringing future impacts into clearer focus.

What then justifies the use of fossil fuels, particularly coal (the dirtiest of them all) anymore?


---

All images in this post are taken from the IPCC's First Assessment Report.

To subscribe, go here.

Comments

Post a Comment

Popular posts from this blog

On Darwin's Lost World - Part II

-
<< Previous page So what do we (did Darwin) know by now (then) ? That living creatures from the very very ancient past (we're talking in terms of millions of years) were often found preserved in the rock record. That we could make out some things about the past environments from these fossils. Fossils showed specific associations: you saw only certain types and groups of fossils in certain suites of rocks (belonging to different periods of geological time). There came a dead end at the base of the Cambrian. Scientists like to call this the Cambrian Explosion today, but back then, many of them were more inclined to dismiss this either as a figment of the imagination of relatively smaller body of researchers, or simply, incomplete/inaccurate science. That the Creator had made us all, was the popular view. 3 theories emerged to explain why we see the Cambrian Explosion (if it even is a real thing!): Charles Lyell Interestingly, it is said that Lyell was...
Read more

On Darwin's Lost World

-
Image
Martin Brasier was a prolific paleontologist. And from what little I know of him, he must have been a pretty cool guy. I recently read his book "Darwin's Lost World" and it was definitely one of the better decisions of my life. On Darwin Thankfully, even the most plebeian of science curricula finds it worthwhile to describe Charles Darwin's scientific accomplishments. To me, all through childhood, Darwin represented my superiority to the apes. When someone said Darwin, I would get a mental picture of an ape gradually turning human. That's an overly simplistic picture, but then again, there is so much to learn about everything  that one doesn't quite know where to start. Source The rock record is the only thing that can give us a picture of the ancient Earth. Most other branches of science can tell you what the Earth is like, and why it is the way it is. But it was Geology that first told us what the Earth was  like, and bits of why it w...
Read more

What is ENSO? Page 2 - SSTs and trade winds

-
Image
  This is Page 2 of the sub-series "What is ENSO?". If you haven't already, please read Page 1 first. For convenience, keep that page open in a different tab. = = = What is ENSO? In the previous post , we learnt to identify ENSO phases from the perspective of sea surface temperature anomalies . In this post, I'm going to answer a question that no one really asked ―  What if I wanted to identify ENSO phases from the perspective of sea surface temperatures (SSTs) instead? What if, for no good reason but because I felt like it, I wanted to do away with the "anomalies" bit? Looking at SSTs instead of SST anomalies makes matters unnecessarily complicated, but we're going to do it anyway because it also teaches us a lot. In the image below, I've plotted SSTs from the HadISST dataset. These are mean SSTs for the months of December, January and February (DJF) over all years from 1872-2009. Why did we select the months of DJF? Because ENSO events can be seen...
Read more