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Lines of evidence that support or refute global warming

Advertisement In Brief Naysayers of climate change, including members of Congress and President Donald Trump, often use weak and long-disproved arguments about alleged holes in the science behind global warming. Human activity is by far the largest source of carbon dioxide pumping into the atmosphere.

The vast majority of climate scientists agree that this contribution is heating the planet and will cause undeniable impact on all ecosystems on Earth. No other explanation—not solar variations or a giant global conspiracy orchestrated by scientists—can account entirely for the fact that the planet is warming and CO2 from human activity is the cause. Multiple lines of evidence, from ice cores to tree rings, support this conclusion.

Most of Donald J. Trump's words and actions concerning climate change have pointed toward his unambiguous disbelief in it. To head the Department of Energy and the Environmental Protection Agency, he picked Rick Perry and Scott Pruitt respectively, both of whom have questioned the role of carbon dioxide in climate change.

Trump's nominees for secretary of agriculture, Sam Clovis, and director of NASA, Jim Bridenstine, have similar views, as do many other appointees to less prominent federal offices. Yet during his first presidential debate with Democratic candidate Hilary Clinton, he denied calling climate change a Chinese hoax.

And when reporters have directly asked White House press secretaries whether Trump denies global warming is real, they have skirted the question.

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The administration seems to want its official stance on the issue to be undeclared and skeptical. Skepticism was the intellectual virtue that U.

But Inhofe had a narrower definition of skeptic in mind: Not everyone who questions climate change science fits that description, of course—some people are genuinely unaware of the facts or honestly disagree about their interpretation. What distinguishes the true naysayers is an unwavering dedication to denying the need for action on the problem, often with weak and long-disproved arguments about supposed weaknesses in the science behind global warming.

What follows is only a partial list of the contrarians' bad arguments and some brief rebuttals of them. Forests remove atmospheric CO2 and offset the nonhuman releases of CO2. Human activity, combined with forest clearing shown herenegates this process, however. Rogers Getty Images Claim 1: Anthropogenic carbon dioxide can't be changing climate, because CO2 is only a trace gas in the atmosphere and the amount produced by humans is dwarfed by the amount from volcanoes and other natural sources.

Water vapor is by far the most important greenhouse gas, so changes in CO2 are irrelevant. Although CO2 makes up only 0.

  1. In some cases, they extend out off the land and into the ocean where they partly float on liquid water.
  2. Building on two previous studies , a landmark 2013 peer-reviewed study evaluated 10,306 scientists to confirm that over 97 percent climate scientists agree, and over 97 percent of scientific articles find that global warming is real and largely caused by humans.
  3. In particular, there do not seem to be clear long-term trends in the cosmic-ray influxes or in the clouds that they are supposed to form, and his model does not explain as greenhouse explanations do some of the observed patterns in how the world is getting warmer such as that more of the warming occurs at night.

Even at that low concentration, CO2 absorbs infrared radiation and acts as a greenhouse gas, as physicist John Tyndall demonstrated in 1859. Chemist Svante Arrhenius went further in 1896 by estimating the impact of CO2 on the climate; after painstaking hand calculations, he concluded that doubling its concentration might cause almost six degrees Celsius of warming—an answer not much out of line with recent, far more rigorous computations.

Contrary to the contrarians, human activity is by far the largest contributor to the observed increase in atmospheric CO2. According to the Global Carbon Project, anthropogenic CO2 amounts to about 35 billion tons annually—more than 130 times as much as volcanoes produce.

True, 95 percent of the releases of CO2 to the atmosphere are natural, but natural processes such as plant growth and absorption into the oceans pull the gas back out of the atmosphere and almost precisely offset them, leaving the human additions as a net surplus.

Climate Science Glossary

Moreover, several sets of experimental measurements, including analyses of the shifting ratio of carbon isotopes in the air, further confirm that fossil-fuel burning and deforestation are the primary reasons that CO2 levels have risen 40 percent since 1832, from 284 parts per million ppm to more than 400 ppm—a remarkable jump to the highest levels seen in millions of years.

Contrarians frequently object that water vapor, not CO2, is the most abundant and powerful greenhouse gas; they insist that climate scientists routinely leave it out of their models. The latter is simply untrue: In fact, water vapor is why rising CO2 has such a big effect on climate. CO2 absorbs some wavelengths of infrared that water does not, so it independently adds heat to the atmosphere. Climatologists therefore categorize water vapor as a lines of evidence that support or refute global warming rather than a forcing factor.

Contrarians who don't see water vapor in climate models are looking for it in the wrong place. Because of CO2's inescapable greenhouse effect, contrarians holding out for a natural explanation for current global warming need to explain why, in their scenarios, CO2 is not compounding the problem.

Climate contrarians argue that variation in solar energy reaching the planet is behind global warming. But human influence has a measurably stronger effect on climate.

Therefore, global warming is a myth. It is hard to know which is greater: Mann and his colleagues or the ultimate insignificance of their argument to the case for climate change. First, there is not simply one hockey-stick reconstruction of historical temperatures using one set of proxy data. Similar evidence for sharply increasing temperatures over the past couple of centuries has turned up independently while looking at ice cores, tree rings and other proxies for direct measurements, from many locations.

Notwithstanding their differences, they corroborate that the planet has been getting sharply warmer. The report placed less faith in the reconstructions back to A.

After the NRC review was released, another analysis by four statisticians, called the Wegman report, which was not formally peer-reviewed, was more critical of the hockey-stick paper. But correction of the errors it pointed out did not substantially change the shape of the hockey-stick graph.

  1. Being prepared for these scenarios is simply smart planning.
  2. Although the magnitudes of future effects are uncertain, human influences on the climate are growing. After the NRC review was released, another analysis by four statisticians, called the Wegman report, which was not formally peer-reviewed, was more critical of the hockey-stick paper.
  3. Svensmark's theory failed to persuade most climatologists, however, because of weaknesses in its evidence. Human activity, combined with forest clearing shown here , negates this process, however.
  4. Scientists should always challenge themselves to improve their understanding. Thousands of studies conducted by researchers around the world have documented changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; ocean acidification; and increasing atmospheric water vapor.
  5. Their so-called consensus on global warming is scientifically irrelevant because science isn't settled by popularity.

In 2008 Mann and his colleagues issued an updated version of the temperature reconstruction that echoed their earlier findings. But hypothetically, even if the hockey stick was busted. The case for anthropogenic global warming originally came from studies of climate mechanics, not from reconstructions of past temperatures seeking a cause. Warnings about current warming trends came out years before Mann's hockey-stick graph.

Even if the world were incontrovertibly warmer 1,000 years ago, it would not change the fact that the recent rapid rise in CO2 explains the current episode of warming more credibly than any natural factor does—and that no natural factor seems poised to offset further warming in the years ahead. Global warming stopped in 1998; Earth has been cooling since then. This contrarian argument might be the most obsolete and unintentionally hilarious.

Here's how it goes: Anyone with even a glancing familiarity with statistics should be able to spot the weaknesses of that argument. Given the extended duration of the warming trend, the expected and observed variations in the rate of increase and the range of uncertainties in the temperature measurements and forecasts, a decade's worth of mild interruption is too small a deviation to prove a break in the pattern, climatologists say.

Climate Change - the REAL inconvenient truth: Scientist claims global warming is NATURAL

If a lull in global warming had continued for another decade, would that have vindicated the contrarians' case? Not necessarily, because climate is complex. For instance, Mojib Latif of the Leibniz Institute of Marine Sciences in Germany and his colleagues published a paper in 2008 that suggested ocean circulation patterns might cause a period of cooling in parts of the Northern Hemisphere, even though the long-term pattern of warming remained in effect.

Fundamentally, contrarians who have resisted the abundant evidence that supports warming should not be too quick to leap on evidence that only hints at the opposite.

That title now goes to 2014. The sun or cosmic rays are much more likely the real causes of global warming. After all, Mars is warming up, too. Astronomical phenomena are obvious natural factors to consider when trying to understand climate, particularly the brightness of the sun and details of Earth's orbit because those seem to have been major drivers of the ice ages and other climate changes before the rise of industrial civilization. Climatologists, therefore, do take them into account in their models.

But in defiance of the naysayers who want to chalk the recent warming up to natural cycles, there is insufficient evidence that enough extra solar energy is reaching our planet to account for the observed rise in global temperatures.

The IPCC has noted that between 1750 and 2005, the radiative forcing from the sun increased by 0. The largest uncertainty in that comparison comes from the estimated effects of aerosols in the atmosphere, which can variously shade Earth or warm it.

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Even granting the maximum uncertainties to these estimates, however, the increase in human influence on climate exceeds that of any solar variation. Moreover, remember that the effect of CO2 and the other greenhouse gases is to amplify the sun's warming. Contrarians looking to pin global warming on the sun can't simply point to any trend in solar radiance: And is what weakens the greenhouse effect a necessary consequence of the rising solar influence or an ad hoc corollary added to give the desired result?

Contrarians therefore gravitated toward work by Henrik Svensmark of the Technical University of Denmark, who argues that the sun's influence on cosmic rays needs to be considered. In Svensmark's theory, the high solar magnetic activity over the past 50 years has shielded Earth from cosmic rays and allowed exceptional heating, but now that the sun is more magnetically quiet again, global warming will reverse.

Svensmark claims that, in his model, temperature changes correlate better with cosmic-ray levels and solar magnetic activity than with other greenhouse factors.

7 Answers to Climate Contrarian Nonsense

Svensmark's theory failed to persuade most climatologists, however, because of weaknesses in its evidence. In particular, there do not seem to be clear long-term trends in the cosmic-ray influxes or in the clouds that they are supposed to form, and his model does not explain as greenhouse explanations do some of the observed patterns in how the world is getting warmer such as that more of the warming occurs at night.

For now, at least, cosmic rays remain a less plausible culprit in climate change. Elevated CO2 makes oceans acidic, which could have irreversible harmful effects on coral reefs, such as coral bleaching shown here. Getty Images And the apparent warming seen on Mars? It is based on a very small base of measurements, so it may lines of evidence that support or refute global warming represent a true trend. Too little is yet known about what governs the Martian climate to be sure, but a period when there was a darker surface might have increased the amount of absorbed sunlight and raised temperatures.

Climatologists conspire to hide the truth about global warming by locking away their data. Their so-called consensus on global warming is scientifically irrelevant because science isn't settled by popularity. It is virtually impossible to disprove accusations of giant global conspiracies to those already convinced of them can anyone prove that the Freemasons and the Roswell aliens aren't involved, too?

Let it therefore be noted that the magnitude of this hypothetical conspiracy would need to encompass many thousands of uncontroversial publications and respected scientists from around the world, stretching back through Arrhenius and Tyndall for almost 150 years.

A conspiracy would have to be so powerful that it has co-opted the official positions of dozens of scientific organizations, including the U. National Academy of Sciences, the U. If there were a massive conspiracy to defraud the world on climate and to what end?

Most of the few statements from those e-mails that critics claimed as evidence of malfeasance had more innocent explanations that make sense in the context of scientists conversing privately and informally. If any of the scientists involved manipulated data dishonestly or thwarted Freedom of Information requests, it would have been deplorable; however, there is no evidence that happened. What is missing is any clear indication of a widespread attempt to falsify and coordinate findings on a scale that could hold together a global cabal or significantly distort the record on climate change.

Climatologists are often frustrated by accusations that they are hiding data or the details of their models because, as NASA's Schmidt points out, much of the relevant information is in public databases or otherwise accessible—a fact that contrarians conveniently ignore when insisting that scientists stonewall their requests.

And because nations differ in their rules on data confidentiality, scientists are not always at liberty to comply with some requests. If contrarians want to deal a devastating blow to global warming theories, they should use the public data and develop their own credible models to demonstrate sound alternatives. Yet that rarely occurs. Notwithstanding some attempts to debunk Oreskes's findings that eventually fell apart, her conclusion stands.

Oreskes's work does not mean that all climate scientists agree about climate change—obviously, some do not although they are very much a minority.