Rise of global temperature and increasing carbon dioxide content of the atmosphere are predicted by the Intergovernmental Panel on Climate Change (IPCC) and other climate alarmists to cause all kinds of undesirable consequences. However, a review of the peer-reviewed scientific literature shows that terrestrial productivity is responding very positively and the planet is greening.

The Center for the Study of Carbon Dioxide and Global Change has a new report which refutes claims that global warming is stressing Earth’s natural and agro-ecosystems by reducing plant growth and development. The report,”The State of Earth’s Terrestrial Biosphere” (133 pages, 2.3Mb) is a meta-analysis, a review, of nearly 400 peer-reviewed scientific studies examining how the productivity of Earth’s plants have responded to the 20^th and now 21^st century rise in global temperature and atmospheric CO_2.

Major findings:

The productivity of the planet’s terrestrial biosphere, on the whole, has been increasing with time, revealing a great greening of the Earth that extends throughout the entire globe. Satellite-based analyses of net terrestrial primary productivity (NPP) reveal an increase of around 6-13% since the 1980s.

There is no empirical evidence to support the model-based claim that future carbon uptake by plants will diminish on a global scale due to rising temperatures. In fact, just the opposite situation has been observed in the real world. Earth’s land surfaces were a net source of CO₂-carbon to the atmosphere until about 1940. From 1940 onward, however, the terrestrial biosphere has become,

in the mean, an increasingly greater sink for CO₂-carbon. Over the past 50 years, for example, global carbon uptake has doubled from 2.4 ± 0.8 billion tons in 1960 to 5.0 ± 0.9 billion tons in 2010.

The observed global greening has occurred in spite of all the many real and imagined assaults on Earth’s vegetation that have occurred over the past several decades, including wildfires, disease, pest outbreaks, deforestation, and climatic changes in temperature and precipitation, more than compensating for any of the negative effects these phenomena may have had on the global biosphere.

There is compelling evidence that the atmosphere’s rising CO₂ content is most likely the primary cause of the observed greening trends.

In the future, Earth’s plants should be able to successfully adjust their physiology to accommodate a warming of the magnitude and rate-of-rise that is typically predicted by climate models to accompany the projected future increase in the air’s CO₂ content. Factoring in plant productivity gains that will occur as a result of the aerial fertilization effect of the ongoing rise in atmospheric CO₂, plus its accompanying transpiration reducing effect that boosts plant water use efficiency, the world’s vegetation possesses an ideal mix of abilities to reap a tremendous benefit in the years and decades to come.

See also:

The Eocene climatic optimum and paradise lost

Climate Change and Biodiversity

For most of the history of Planet Earth, the temperature has been much warmer than it is now. Climate alarmists claim that if we allow the planet to warm even 2ºC (3.6ºF), as if we could actually prevent that, then all hell will break loose. So let’s look at a time in Earth’s history when it was even warmer and see how things were. I refer to the Eocene climatic optimum, 50-to 33 million years ago.

During the Eocene, average global temperature is estimated to have been at least 18ºF higher than the current average, atmospheric carbon dioxide levels are estimated to have been about 3,000 ppm, about eight times higher than now, and sea level was about 200 feet higher because for much of the time, there was little or no ice at the poles. Even with up to 3,000 ppm carbon dioxide in the atmosphere, the oceans never became acidic, although the pH was slightly lower than it is now. These estimates are based on geologic evidence such as fossils, sedimentation types and rates, and isotope studies.

Science writer Paul MacRae says: “Curiously, while alarmists warn about the horrors of returning to the climate of millions of years ago, paleoclimatologists tell a different story. They more often see our earlier planet as a ‘paradise,’ even ‘paradise lost.’”

During the Eocene climatic optimum, the planet was “verdant and productive,” covered with luxuriant vegetation. MacRae notes that even prominent climate alarmist, Tim Flannery says in his book, The Eternal Frontier, that North America was a tropical paradise.

Sara Stein describes the Eocene ( in The Evolution Book): “The world that all the little brown furry things inherited from the dinosaurs was paradise. The climate was so mild that redwoods, unable now to live much further north than California’s pleasant coast, grew in Alaska, Greenland, Sweden, and Siberia. There was no ice in the Arctic. Palm trees grew as far north as 50 degrees latitude, roughly the boundary between the United States and Canada. Below that subtropical zone—that was similar to Florida’s landscape today—was a broad band of tropical rain forest.”

The “little brown furry things” refers to the fact that modern mammal species arose during the Eocene.

Although some climate alarmists insist that a warmer world will be plagued by droughts and deserts, the Earth in the Eocene was a much wetter world which supported tropical vegetation. Isotope studies suggest that the warm Eocene had a “balanced, subtropical hydrologic cycle and wetter mid-high latitudes” and tropics with “substantially decreased evaporation and increased precipitation” compared to current conditions. And “even though the Eocene was undeniably hotter than today’s climate, the tropics were probably not as warm as previously thought. That, plus a stable but enhanced hydrologic cycle, made Earth a more congenial planet to live on.”

Alas, paradise was not to last. Toward the end of the Eocene, the continents of South America and Australia had separated sufficiently from Antarctica to provide a deep water connection between the Pacific and Atlantic Oceans which changed circulation patterns and hence climate. Celestial mechanics and our solar system’s position in the galaxy were also working against paradise (see: Ice Ages and Glacial Epochs) and Earth began its long, slow plunge into another Ice Age, making the current average global temperatures the coldest in nearly 300 million years.

Return to a warmer wetter planet really doesn’t sound as catastrophic as some make it out to be.

“Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory.” -Stephen Hawking

“It does not matter who you are, or how smart you are, or what title you have, or how many of you there are, and certainly not how many papers your side has published, if your prediction is wrong then your hypothesis is wrong. Period.” -Richard Feynman

“Who would dare assert that we know all there is to be known?” -Galileo Galilei

On many of my posts about climate change, I get comments from believers in catastrophic anthropogenic global warming that take issue with what I have written.  That’s fine.  But, instead of presenting facts to support their case, many of these commenters resort to invoking the myth alleging that about 98% of climate scientists say human carbon dioxide emissions are the major cause of recent warming. This alleged consensus, they say, must mean it’s true and should end all argument.  Some of these commenters also seem to be confused about cause and effect, and so conflate the perceived incidence of warming or cooling with attribution of cause.

So let’s look first at where these consensus numbers came from and then I will comment more generally on consensus in science.

One source was from a study by Peter Doran and Maggie Zimmerman at the University of Illinois. (See here and here.) They emailed 10,257 scientists and asked two questions:

Question 1: “When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?” I would answer that temperatures have risen because in the 20^th Century the planet warmed from the depths of the “Little Ice Age.” The answer to this question is verifiable by observation of physical evidence.

Question 2 (the controversial question): “Do you think human activity is a significant contributing factor in changing mean global temperatures? The researchers didn’t define “significant.” This question solicits an opinion. The basic premise of the question has not been verified by physical evidence.

Of the original 10,257 scientists queried, 3,146 responded. Of those, Doran and Zimmerman whittled the number down to 77 who had been successful in getting more than half of their papers recently accepted by peer-reviewed climate science journals. Of the 77, 75 answered “yes” to question 2,that’s 97.4%. So, in that study the whole 98% claim is based on 75 positive answers out of 3,146 respondents.

The other possible source for the consensus myth is a paper by Anderegg et al, in PNAS. In that study, the researchers didn’t bother to poll scientists, rather they scanned the literature and constructed a “database of 1,372 climate researchers based on authorship of scientific assessment reports and membership on multi-signatory statements about ACC [anthropogenic climate change]” as outlined by the Intergovernmental Panel on Climate Change. The researchers then arbitrarily assigned “expert” status to those who had published at least 20 papers. That cut the number of “experts” to 908. In the supporting material at the end of the paper we find that of the original 1,372 researchers, 619 were contributors to the IPCC’s Fourth Assessment report, and 212 were signatories to the UN’s Bali declaration. After culling duplicate names, the paper’s authors wound up with 472 “experts” out of tens of thousands of practicing researchers.

We see from the two studies, therefore, that this claim of a 98% consensus comes from carefully culled researchers, most of whom worked on the IPCC reports, are said to believe that humans are the principal cause of climate change. The 98% consensus consists of researchers who have a vested interest in continuing the myth of significant global warming caused by human carbon dioxide emissions. Follow the money. The 98% consensus is just another manipulated number pulled out of the air.

Now, let’s turn to a more general discussion of consensus.

Dr. Judith Curry, Chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology, has a long paper on consensus in climate science. She begins by saying: “The manufactured consensus of the IPCC has had the unintended consequences of distorting the science, elevating the voices of scientists that dispute the consensus, and motivating actions by the consensus scientists and their supporters that have diminished the public’s trust in the IPCC.”

She goes on the write: “With genuinely well-established scientific theories, ‘consensus’ is not discussed and the concept of consensus is arguably irrelevant… While a consensus may arise surrounding a specific scientific hypothesis or theory, the existence of a consensus is not itself the evidence.” And she notes: “If the objective of scientific research is to obtain truth and avoid error, how might a consensus seeking process introduce bias into the science and increase the chances for error? ‘Confirmation bias’ is a well-known psychological principle that connotes the seeking or interpreting of evidence in ways that are partial to existing beliefs, expectations, or an existing hypothesis. Confirmation bias usually refers to unwitting selectivity in the acquisition and interpretation of evidence.”

There are some famous failures of consensus in history. The pre-eminent one was the belief that the Earth was the center of the universe. That was the prevailing consensus 500 years ago. That consensus was shown to be in error, first by Nicolaus Copernicus and later by Galileo, Kepler, and Newton.

In 1912, Alfred Wegener, building on earlier work by Frank Bursley Taylor, proposed that the continents did not have a permanent spacial relationship to each other, i.e., there was continental drift. Wegener could not, however, provide a reasonable mechanism for his hypothesis, therefore the consensus, for 50 years, was that he was wrong. By the 1960s, geological research did provide the mechanism and Wegener’s continental drift became part of the larger theory of plate tectonics.

Those who credulously invoke the “ 98% consensus” as an argument are displaying an ignorance of the facts and of how science works.  I refer you to Michael Crichton who said:

“I regard consensus science as an extremely pernicious development that ought to be stopped cold in its tracks. Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled. Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you’re being had.”

“Let’s be clear: The work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science consensus is irrelevant. What is relevant is reproducible results. The greatest scientists in history are great precisely because they broke with the consensus.”