Fifty years ago today, as the American Association for the Advancement of Science highlighted, US president Lyndon Johnson’s science advisory committee sent him a report entitled Restoring the Quality of Our Environment. The introduction to the report noted:
Pollutants have altered on a global scale the carbon dioxide content of the air and the lead concentrations in ocean waters and human populations.
The report included a section on atmospheric carbon dioxide and climate change, written by prominent climate scientists Roger Revelle, Wallace Broecker, Charles Keeling, Harmon Craig, and J Smagorisnky. Reviewing the document today, one can’t help but be struck by how well these scientists understood the mechanisms of Earth’s climate change 50 years ago.
The report noted that within a few years, climate models would be able to reasonably project future global surface temperature changes. In 1974, one of its authors, Wallace Broecker did just that in a paper titled Climatic Change: Are We on the Brink of a Pronounced Global Warming?.
You can read the details about this paper and Broecker’s modeling here and in my book Climatology versus Pseudoscience. His model only included the effects of carbon dioxide and his best estimates of natural climate cycles. It didn’t include the warming effects of other greenhouse gases, or the cooling effects of human aerosol pollution, but fortunately for Broecker those two effects have roughly canceled each other out over the past 40 years.
Broecker’s model predicted the global warming anticipated by 2015 both from carbon pollution alone, and when including his best estimate of natural climate cycles. In the figure below, the carbon-caused warming is shown in blue, and in combination with natural cycles (which Broecker turns out not to have represented very accurately) in green, as compared to the observed global surface temperatures from NOAA in red. As you can see, the climate model predictions from over 40 years ago turned out to be remarkably accurate.
The 1965 report also debunked a number of myths that climate contrarians continue to repeat to this day. For example, the first section of the climate chapter is titled Carbon Dioxide from Fossil Fuels – the Invisible Pollutant. Although the US supreme court ruled that carbon dioxide is a pollutant in a landmark 2007 case, many contrarians object to this description. Nevertheless, climate scientists realized a half century ago that human carbon emissions qualify as pollution due to the dangers they pose via climate change.
The report noted that although carbon dioxide is an invisible “trace gas” – meaning it comprises a small percentage of the Earth’s atmosphere as a whole – it can nevertheless have significant impacts on the climate at these seemingly low levels. As the scientists wrote:
Only about one two-thousandth of the atmosphere and one ten-thousandth of the ocean are carbon dioxide. Yet to living creatures, these small fractions are of vital importance … Within a few short centuries, we are returning to the air a significant part of the carbon that was slowly extracted by plants and buried in the sediments during half a billion years.
Contrarians today often repeat the myths that because carbon dioxide is invisible and only a trace gas, it can’t possibly cause significant climate change. This report demonstrates that scientists understood the greenhouse effect better 50 years ago than these contrarians do today.
The report documented the several different lines of evidence that prove the increase in atmospheric carbon dioxide is entirely human-caused, concluding:
We can conclude with fair assurance that at the present time, fossil fuels are the only source of CO2 being added to the ocean-atmosphere-biosphere system.
This is yet another fact understood by climate scientists 50 years ago that some contrarians, including a few favorite contrarian climate scientists like Roy Spencer and Judith Curry, continue to cast doubt upon to this day.
The report also projected how much the atmospheric carbon dioxide level would increase in the following decades.
Based on projected world energy requirements, the United Nations Department of Economic and Social Affairs (1956) has estimated an amount of fossil fuel combustion by the year 2000 that with our assumed partitions would give about a 25 percent increase in atmospheric CO2, compared to the amount present during the 19th Century.
A 25% increase from pre-industrial levels would result in about 350 ppm of carbon dioxide in the atmosphere. The United Nations underestimated the growth in fossil fuel combustion, because the actual carbon dioxide level in 2000 was 370 ppm.
In addition to rising temperatures, the report discussed a variety of “other possible effects of an increase in atmospheric carbon dioxide”, including melting of the Antarctic ice cap, rise of sea level, warming of sea water, increased acidity of fresh waters (which also applies to the danger of ocean acidification, global warming’s evil twin), and an increase in plant photosynthesis.
These climate scientists warned President Johnson in 1965 not just of the dangers associated with human-caused global warming, but also that we might eventually have to consider geoengineering the climate to offset that warming and the risks that we’re causing by inadvertently running a dangerous experiment with the Earth’s climate.
Through his worldwide industrial civilization, Man is unwittingly conducting a vast geophysical experiment. Within a few generations he is burning the fossil fuels that slowly accumulated in the earth over the past 500 million years … The climatic changes that may be produced by the increased CO2 content could be deleterious from the point of view of human beings. The possibilities of deliberately bringing about countervailing climatic changes therefore need to be thoroughly explored.
Fifty years later, the impending Paris international climate negotiations represent our last chance to heed the expert counsel about the dangers posed by human-caused climate change before we’re fully committed to the deleterious consequences that climate scientists have been warning us about for a half century.
That’s why more than 1,500 academics from around the world have signed an open letter asking world leaders and delegates at Paris to take vigorous action now in order to avoid a future of catastrophic global warming.
STEVE INSKEEP, HOST:
Researchers identified a provocative way to fight climate change.
DAVID GREENE, HOST:
Many people want to know what they can do about a vast global problem - maybe switch to an electric car, maybe eat less meat, maybe hang up clothes to dry.
INSKEEP: Well, Kimberly Nicholas of the University of Lund in Sweden wanted to help people make smart choices. And she found many of those efforts we just mentioned make only a slight difference in a family's carbon footprint, as it's called. People make a bigger impact with one thing that they choose to do - or not do.
KIMBERLY NICHOLAS: The single biggest impact that we found was from having a child. The reason for that is because that measure accounts for all the choices that that child would make in their life - and their descendants.
INSKEEP: What did you think and feel when you reached that conclusion?
NICHOLAS: Well, I think - I knew this would be a sensitive topic to bring up. Certainly, it's not my place, as a scientist, to dictate choices for other people. But it is my place to do the analysis and report it fairly. You know, something really important we found is that most government recommendations weren't really talking about what made the biggest difference. And they weren't quantifying how big of a difference it made.
INSKEEP: May I ask a personal question?
NICHOLAS: You may.
INSKEEP: You have kids?
NICHOLAS: I don't. It's a choice I'm thinking about right now and discussing with my fiance.
INSKEEP: Oh, congratulations. You're getting married. That's great.
NICHOLAS: Thank you. Yeah, maybe some people are learning that now. But yes, it is great news. And he is wonderful. And of course, having a child is one of the most personal decisions people can make. And there are many, many factors that go into it for everyone, including us. For us, because we care so much about climate change, it is a factor we're considering. But it's not the only one.
INSKEEP: I'm thinking about the implications here, though, because if a few individuals make a choice to have no children or fewer children than they otherwise would, that's going to make no effective difference. This is something that millions or billions of people would have to decide, I would think, in order to make a significant difference. Do you think that some governments somewhere should be pressing their citizens in some way?
NICHOLAS: No, I really don't think that that's the way to interpret our study. And I think that the decision to become a parent or to have a child is a really personal decision. And I think the way people relate to it in terms of climate change depends on their view about climate change. If they don't believe or they don't know the science, I think it makes them angry because they feel like their rights are being taken away. I think if they do know the science and are overwhelmed by it, they feel guilt or despair.
And I think if they know the science, recognize how serious the risk is and how urgent it is that we reduce emissions but they want a child and they want to raise that child in a safe planet, then having a child in that case is a vote of hope. It's a vote that the world is going to be a better place and that we can actually tackle this challenge. I think making that decision means a big responsibility.
INSKEEP: I can imagine people hearing about your study and being darkly suspicious and thinking, oh, here's somebody who's trying to set the stage intellectually for a one-child policy, like they had in China once upon a time or some kind of forced, government family planning.
NICHOLAS: No (laughter). That's certainly not my secret ambition. You know, I worry about people accusing me of that, but it's not the case. I felt that it's something we really have to look at because we know that how many people there on Earth affects the climate. And if people want to know what they can do to reduce their climate emissions, then we have to look at that question, too.
INSKEEP: You just want us to be conscious of what we're doing, it sounds like.
NICHOLAS: I do. I think there's a huge information gap. I know - I mean, as a scientist, I think in data and numbers and ratios. And I know that it's not information that changes hearts and minds, but information is necessary to start conversations.
INSKEEP: And our conversation with researcher Kimberly Nicholas came via Skype.
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