The theoretical global warming projections are now being compared to reality measurements, which really can’t be readily contested. Here’s a summary, followed by some suggestions about what each of us can actually do to improve the situation.
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Global Warming’s Worst-Case Projections Look Increasingly Likely
A new study based on satellite observations finds that temperatures could rise nearly 5 °C by the end of the century.
by James Temple
MIT Technology Review
December 6, 2017
Global warming’s worst-case projections look increasingly likely, according to a new study that tested the predictive power of climate models against observations of how the atmosphere is actually behaving.
The paper, published on Wednesday in Nature, found that global temperatures could rise nearly 5 °C by the end of the century under the the UN Intergovernmental Panel on Climate Change’s steepest prediction for greenhouse-gas concentrations. That’s 15 percent hotter than the previous estimate. The odds that temperatures will increase more than 4 degrees by 2100 in this so-called “business as usual” scenario increased from 62 percent to 93 percent, according to the new analysis.
Climate models are sophisticated software simulations that assess how the climate reacts to various influences. For this study, the scientists collected more than a decade’s worth of satellite observations concerning the amount of sunlight reflected back into space by things like clouds, snow, and ice; how much infrared radiation is escaping from Earth; and the net balance between the amount of energy entering and leaving the atmosphere. Then the researchers compared that “top-of-atmosphere” data with the results of earlier climate models to determine which ones most accurately predicted what the satellites actually observed.
The simulations that turned out to most closely match real-world observations of how energy flows in and out of the climate system were the ones that predicted the most warming this century. In particular, the study found, the models projecting that clouds will allow in more radiation over time, possibly because of decreased coverage or reflectivity, “are the ones that simulate the recent past the best,” says Patrick Brown, a postdoctoral research scientist at the Carnegie Institution and lead author of the study.
This cloud feedback phenomenon remains one of the greatest areas of uncertainty in climate modeling.
The UN’s seminal IPCC report relies on an assortment of models from various research institutions to estimate the broad ranges of warming likely to occur under four main emissions scenarios. In another key finding, the scientists found that the second-lowest scenario would be more likely to result in the warming previously predicted under the second-highest by 2100. In fact, the world will have to cut another 800 gigatons of carbon dioxide emissions this century for the earlier warming estimates to hold.
(By way of comparison, total greenhouse-gas emissions stood at about 49 gigatons last year.)
Various politicians, fossil-fuel interest groups, and commentators have seized on the uncertainty inherent in climate models as reasons to doubt the dangers of climate change, or to argue against strong policy and mitigation responses. Brown says …
“This study undermines that logic.
There are problems with climate models,
but the ones that are most accurate are the
ones that produce the most warming in the future.”
In fact, the new paper is the latest in a growing series that project larger impacts than previously predicted or conclude that climate change is unfolding faster than once believed.
The goal of the research was to evaluate how well various climate models work, in hopes of “narrowing the range of model uncertainty and to assess whether the upper or low end of the range is more likely,” Brown wrote in an accompanying blog post.
Ken Caldeira, a climate researcher at Carnegie and coauthor of the paper, says the growing body of real-world evidence for climate change is helping to refine climate models while also guiding scientists toward those that increasingly appear more reliable for specific applications.
But an emerging challenge is that the climate is changing faster than the models are improving, as real-world events occur that the models didn’t predict. Notably, Arctic sea ice is melting more rapidly than the models can explain, suggesting that the simulations aren’t fully capturing certain processes. Caldeira says …
“We’re increasingly shifting from a mode
of predicting what’s going to happen to a
mode of trying to explain what happened.”
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The question for me is: “What can each of us do, as individuals … trying to live a decent life in accordance with what our planet provides?”
If I were head of a major corporation that’s been producing and selling oil products for over a century – with which we’ve enjoyed a better quality of life experience – then all this opposition to fossil fuels would be a threat to my company’s future. That’s dissonance. And there are many ways to reduce dissonance.
- Discredit the source, “I see alternative facts from other sources that are more reliable – and less biased.”
- Discredit the research, “There are other models that are more accurate.”
- Or I could just bi-pass the reports by raising other issues, such as “the economy” or “trade agreements,” or “international relations.”
As head of that corporation, I’d also make generous contributions to political candidates who might support my business through legislation.
However, if I ask myself what the negative effects might be if I – as a simple individual trying to live a decent, joyful life – make changes that drastically reduce my use of fossil fuels, I can’t find any.
My photovoltaic panels provide me with all the power I need, and for less money.
My electric car is fun to drive and costs a fraction, per mile, of even the most efficient gas-powered car. And my car maintenance costs – given that an electric car has no carburetor to adjust or spark plugs to change, or muffler to replace, or engine to clean – are also a ridiculously small fraction of any gas car.
And, less immediately measurable, we’d have better air quality and less respiratory disease than we have now. People boast about China’s progress and robust economy, but they can rarely see the sky, due to smog. And Delhi, India, often has to cancel airline flights. And Phoenix has also had to cancel flights because planes can’t operate above temperatures they were experiencing.
And food production will also suffer as temperatures escalate. And making these changes is easier if we’re in a community of others who are also making these changes … rather than doing it as a “lone wolf.” Each of us has to ask these questions, then decide what’s truly best for our lives and those of our families. And given reports such as this one, we need to act sooner than later.