Though a bit of misinformation about NASA's supposedly having said that the burning of fossil fuels actually cools the Earth's climate dates back to December 2015, it was recently dug up and reposted on the conservative website Louder with Crowder on 27 January 2017. In the site's original post (published on 21 December 2015), Courtney Kirchoff wrote:
The latest talking point to march to its death? Fossil fuels cause global warming. Because they don’t. In fact, NASA says they’re actually causing temporary global cooling. That sound you hear? Dying dreams. Crashing Priuses.
The information Kirchhoff so smugly cited to support this assertion was not a NASA study itself, but a story published in the U.K. tabloid Express by their “science and paranormal correspondent” Jon Austin, whose more recent work includes hard-hitting scientific investigations such as “Moon Is Hollow 'Death Star' Like Alien Base, Says Shocking Google Image Theory”, “Was This 'Floating City' That Appeared Over China a Glimpse Into 'Another Dimension'?” and “Are Aliens Draining Our Solar Energy? Images of Monster UFOs Circling Sun Emerge.”
In that Express piece, also from 21 December 2015, Austin wrote:
Major theories about what causes temperatures to rise have been thrown into doubt after NASA found the Earth has cooled in areas of heavy industrialisation where more trees have been lost and more fossil fuel burning takes place.
Environmentalists have long argued the burning of fossil fuels in power stations and for other uses is responsible for global warming and predicted temperature increases because of the high levels of carbon dioxide produced — which causes the global greenhouse effect.
While the findings did not dispute the effects of carbon dioxide on global warming, they found aerosols — also given off by burning fossil fuels — actually cool the local environment, at least temporarily.
This was a wholly dishonest and inaccurate representation of both the purpose of the referenced study and the nature of its results. The study, which neither of the above writers appeared to have read, aimed to improve the accuracy of a key metric derived from climate models.
Climate modeling has as its goal the creation of a plausible simplification of the global climate system based on physics and historical data. These models are refined and tested, over time, by comparing multiple iterations of their results from a known historical starting point, and analyzed to see how well the models output matches the historical record. One of the most important things scientists attempt to ascertain with these global models is what is known as climate sensitivity — essentially a measurement of how much our planet warms as a result of a doubling of CO2.
Getting the most accurate estimate of that metric, climate sensitivity, is in many senses the holy grail of climate modelers, because it is the key to developing confident predictions about future warming. Since the climate system is massive and affected by both short term and long term processes, sensitivity is often defined on two timescales: "The transient climate response (TCR: the warming after 70 years of CO2 concentrations that rise at 1% per year), and the equilibrium climate sensitivity (ECS: the equilibrium temperature change following a doubling of CO2 concentrations)."
The underlying study, published on 14 December 2015 in the journal Nature Climate Change, attempted to refine estimates of those two variables by breaking a number of different aspects of the climate system into individual inputs, such as aerosols from pollution, ozone, solar variations, etc. This type of precision model testing is something made possible only recently by the collection of large datasets that document or estimate past variations in these more obscure metrics:
The NASA Goddard Institute for Space Studies (GISS) modelling group performed ‘historical’ simulations using model version GISS-E2-R [one of many models used by the IPCC] spanning 1850–2005, driven by estimates of relevant natural and external forcings. Multiple simulations over the same time period using single forcings or combinations of forcings were also [compared to historical data], including simulations forced by only well-mixed greenhouse gases, anthropogenic aerosols, ozone, solar variations, volcanoes, or land-use changes.
These unique ensembles allow us to replicate climate sensitivity calculations in a ‘perfect model’ framework, in which we have all the information we need to determine transient and equilibrium sensitivities using previously published methods, which can be compared to the actual TCR and ECS of the GISS-E2-R model.
What researchers found in comparing models using only CO2 forcing estimates to models using different components individually was that the models based on separate components were less sensitive (i.e., showed a more dampened response to increased CO2) than ones that used the simplified inputs:
GISS ModelE2 is more sensitive to CO2 alone than it is to the sum of the forcings that were important over the past century. This is largely a result of the low efficacy of ozone and volcanic forcings and the high efficacy of aerosol and LU forcing (which have had a cooling effect over the historical period), although further study is needed to explore model differences in simulating efficacies and to enhance confidence in these estimates.
The implication of this finding, the authors stated, was that:
Climate sensitivities estimated from recent observations will therefore be biased low in comparison with CO2-only simulations owing to an accident of history: when the efficacies of the forcings in the recent historical record are properly taken into account, estimates of TCR and ECS must be revised upwards. Accounting for this results in recent historical estimates for TCR and ECS that are more consistent with constraints based on palaeoclimate data and process-based constraints from modern climatology.
In other words, the study found that estimates of how much global warming could be expected in the long term from release of CO2 used in current climate models (which are frequently derived from relatively recent satellite data), are actually too low, because they are masked by a stronger than assumed short-term dampening effect from fossil fuel aerosols (particulate matter that serve to block incoming sunlight) and the effect of deforestation (which can sometimes cause more energy to be reflected back into space).
The authors are actually arguing that future temperatures could well be warmer than predicted as a result of what they learned from the study. In a NASA press release, Gavin Schmitt, one of the authors of this study, said:
If you've got a systematic underestimate of what the greenhouse gas-driven change would be, then you're systematically underestimating what's going to happen in the future when greenhouse gases are by far the dominant climate driver.
What the study did not find, however, was evidence that fossil fuels cool the planet. They don’t. The planet is getting warmer and is doing so, broadly, in concert with rising fossil fuel emissions.
Additionally, this study (counter to the implication of the viral news reports) didn’t “discover” the effects of aerosols, nor did it discover the effects of deforestation on the climate system. From a general standpoint, the dampening effect of aerosols and deforestation on Earth’s climate have been known for decades.
A 1967 paper in the journal Science, for example, attempted to calculate the effect of aerosols on temperature, suggesting that aerosols may have been responsible for a perceived cooling trend in spite of rising CO2 temperatures — the very dynamics the study in question attempted to elucidate through modeling:
We suggest that the effects of man's pollution of his environment are monotonically increasing along with the world population. The emission of long-lived aerosol, keeping pace with the accelerated worldwide production of CO2 may well be leading to the decrease in worldwide air temperature in spite of the apparent buildup of CO2. In any case, it is clear that in this "large-scale geophysical experiment" in which human beings are engaged, the course of atmospheric turbidity must be documented with concern.
The famed science communicator Carl Sagan himself pontificated over the various ways in which deforestation could affect Earth’s climate in a 1979 paper also published in Science, figuring that it had any effect it would be to cool the planet:
The massive extinction of equatorial forests [could potentially] have important implications for the global as well as the regional climate. We suggest that major deforestation in equatorial latitudes may be a matter of international concern, and note the systematic destruction of the Amazon jungle now under way, the activity of several corporations in a single country.
This activity may even be desirable, as a counterbalance to greenhouse heating of the earth; but it would seem prudent, on an issue of possible global importance, to study its implications in some detail before proceeding unilaterally.
The issue in NASA’s 2015 paper was not to test these common knowledge climate effects, but to use new historical records to improve climate modelers’ ability to create accurate estimates of climate sensitivity over both short and long timescales. Indeed, scientists are not debating the questions viral stories like those written by Kirchoff suggest: the climate warming potential of burning fossil fuels has been known for well over a century.