Rapid Paleocene Global Warming Caused Diversity Explosion

One of the scary predictions made about the impact of global warming is the extinction of many current species leading to a crisis in biological diversity. Like most of the speculative effects of global warming, this prediction is not only without scientific basis, it is precisely backward. A new paper in the journal Science, studying the impact of rapid global warming at the Paleocene-Eocene boundary, show that rapid tropical forest diversification occurred without plant extinction. Moreover, diversity seemed to increase at higher temperatures, contradicting previous assumptions that tropical flora will succumb if temperatures become excessive. The tropical rainforest was able to flourish under elevated temperatures and high levels of atmospheric carbon dioxide, in contrast to speculation that tropical ecosystems were severely harmed by the heat.

The Paleocene-Eocene Thermal Maximum (PETM) 56.3 million years ago was a unique episode of rapid global warming (~5°C). It is often used as an ancient analog for future global climate by those hyping catastrophic climate change. Though there is little chance that human CO2 emission could cause such and event, that has not prevented the global warming gloom and doom crowd from holding up the threat of a possible second PETM event to bolster their socioeconomic agenda for the world. Supposedly, a PETM replay would bring with it all sorts of calamitous environmental consequences.

Now, a number of those dire, nature ravaging predictions made by global warming scaremongers have been revealed as the crap-science propaganda that they are. In a new journal paper, “Effects of Rapid Global Warming at the Paleocene-Eocene Boundary on Neotropical Vegetation,” Carlos Jaramillo et al. present their analysis of the effects of rapid global warming during the Paleocene-Eocene Thermal Maximum (PETM) 56.3 million years ago. Here is how they introduced their work in the paper's abstract:

We investigated the tropical forest response to this rapid warming by evaluating the palynological record of three stratigraphic sections in eastern Colombia and western Venezuela. We observed a rapid and distinct increase in plant diversity and origination rates, with a set of new taxa, mostly angiosperms, added to the existing stock of low-diversity Paleocene flora. There is no evidence for enhanced aridity in the northern Neotropics. The tropical rainforest was able to persist under elevated temperatures and high levels of atmospheric carbon dioxide, in contrast to speculations that tropical ecosystems were severely compromised by heat stress.

Promoters of catastrophic climate change have often warned that rising global temperatures would decimate the natural world, striking down species right and left, leaving world biological diversity dangerously depleted. The most vulnerable of habitats were taken to be the world's rainforests, those hot, humid bastions of teaming jungle life. Rains would fail and the nurturing forests would die, taking the indigenous animal life with them. Now we know this to be yet another warmist fairy tail.


The world's rainforests are reservoirs of diversity.

“Efforts to understand the impact of climate change on terrestrial environments have focused on mid- to high-latitude localities, but little is known of tropical ecosystems during the PETM,” state the authors. “Tropical temperature change is poorly constrained, but, given the magnitude of temperature change elsewhere, tropical ecosystems are thought to have suffered extensively because mean temperatures are surmised to have exceeded the ecosystems’ heat tolerance.” But, as the study details, this was most certainly not the case.

The researchers examined data from three tropical terrestrial PETM sites from Colombia and Venezuela. The map below shows the Late Paleocene location of the studied sections (map after C. R. Scotese). Note that the northern Andes had not yet been uplifted and most of Central America was still underwater.


Geographical location of the studied sections.

At two of the sites, labeled Mar 2X and Riecito Mache, plant diversity was inferred from ancient pollen. These data show relatively low diversity during the Late Paleocene, followed by a significant increase during the PETM. Low-diversity Paleocene floras followed an increase in Early Eocene diversity had been previously observed in tropical South America, but the timing of the diversity changes was not accurately established.

While species continued to go extinct during the PETM—as they have since the beginning of life on Earth—there was nothing out of the ordinary about the extinction rate when compared with surrounding time periods. And while the extinction rate remained fairly constant the addition of new specie, called the origination rate, spiked during the sudden warmth of the PETM. The extinction and origination rates are shown in the figure below, taken from the report.


Extinction and origination rates.

This definitely flies in the face of common climate science wisdom. The authors note: “Many have argued that tropical communities live near their climatic optimum and that higher temperatures could be deleterious to the health of tropical ecosystems. Indeed, tropical warming during the PETM is surmised to have produced intolerable conditions for tropical ecosystems, although 31° to 34°C is still within the maximum tolerance of leaf temperature of some tropical plants.”

Those widely held beliefs have now been debunked. Of course, this news comes as no surprise to many scientists, particularly those who actually study the effects of temperature and carbon dioxide on plants. Jon Lloyd and Graham D Farquhar noted in the Philosophical Transactions of the Royal Society B, “we find no evidence for tropical forests currently existing ‘dangerously close’ to their optimum temperature range.”

“Greenhouse experiments have shown that high levels of CO2 together with high levels of soil moisture improve the performance of plants under high temperatures, and it is possible that higher Paleogene CO2 levels contributed to their success,” note Jaramillo et al. This echos what several authorities have pointed out in the past: CO2 is plant food. As long as there is sufficient precipitation, and the study found that rainfall did not diminish, plants can do very well with elevated carbon dioxide levels.

This conclusion is not surprising, since lead author Jarmillo, writing with Milton J. Rueda and Germán Mora, had previously reported that “A good correlation between diversity fluctuations and changes in global temperature was found, suggesting that tropical climate change may be directly driving the observed diversity pattern.” This correlation has been known by paleobiologists for some time (see “Cenozoic Plant Diversity in the Neotropics” in the March 31, 2006, issue of Science). Of course, with fluctuating temperatures come fluctuating CO2 levels.


The PETM warmth helped orchids to flourish.

“Overall diversity and composition analysis suggest that the onset of the PETM is concomitant with an increase in diversity produced by the addition of many taxa (with some representing new families) to the stock of preexisting Paleocene taxa,” the new study concludes. What's more, “this change in diversity was permanent and not transient, as documented for temperate North America.” Not just a flash in the pan, the sudden increase in temperatures during the PETM actually caused a lasting increase in diversity.

As usual, the climate alarmist party line is not only wrong but dead wrong. Higher global temperatures and elevated CO2 levels were good for nature 50 million years ago and certainly won't harm nature today. In fact, one of the observed impacts of the PETM warming was the spread of orchids. Perhaps the IPCC secretly hates flowers. Regardless, the myth that higher levels of CO2 and higher temperatures will destroy the tropical rainforests has been shown to be climate alarmist disinformation.

Be safe, enjoy the interglacial and stay skeptical.

One Wonders What Else They are Wrong About!!

…….uummmm, new animal phyla suddenly spike during warming of PETM, sounds suspiciously like they were designed to do that.

Mark in Durango

Good questions

Some good questions. I have written often about the PETM and find it a fascinating example of just how stable Earth's climate system is. Evidently climate scientists also find it an interesting subject since new papers continue to appear in journals about it. Here are a few points I have gleaned from my study of the PETM:

  • Estimates of how large a pulse of CO2/CH4 was released to initiate the PETM varies widely. The estimates all tend to be in the range of 1,200 – 5,000 gigatons of carbon with 2,000 gigatons cited most often and at least one estimate as high as 10,000 gigatons. Based on the upper limit temperature rise, ~9°C, atmospheric carbon dioxide levels more than doubled.

  • Whether that release came all at once or over a period of several millennia is also a matter of speculation. The problem is that when trying to measure time spans at a remove of 55 million years science simply cannot resolve dates any closer than thousands of years. They are sure that it happened over a time span less than 10,000 but how much less is pure conjecture. Some papers say the release could have taken less than 1,000 years, instantaneous for all practical purposes, but we have no way of resolving the time span precisely.

  • Regardless of whether the hypothesized GHG release happened all at once or took thousands of years the result would have been pretty much the same. Gases in the atmosphere are well mixed, meaning any warming effect should have occurred quickly and globally. However, Earth's climate system has a great deal of hysteresis: the oceans, particularly the cold deep waters around Antarctica, act as a huge heat sink for the planet, as do the large glacial ices sheets in Antarctica and Greenland. Single release or ramped up over thousands of years, the global temperature increase would not have been instantaneous but rather a moderated rise that would slow as it approached the new thermal equilibrium point (what a control engineer would call an over-damped system). Again, there are problems resolving the actual timeline.

  • The pattern of greater relative warming in what are now the temperate latitudes, with the equatorial regions remaining largely unchanged, has been observed over other historical periods as well. This is probably because the Earth system is quite effective at transporting heat energy away from the tropics to higher latitudes.

  • People get hung up on doubling atmospheric CO2 levels. The first thing to know is that the effect of doubling atmospheric CO2 very much depends on where you start from. Going from 250 ppm to 500 ppm will have a much bigger effect in terms of total temperature rise than going from 500 ppm to 1,000 ppm. As noted, the starting point for the PETM episode was considerably higher than modern levels, implying that it would take significantly more CO2 to cause the observed jump in temperatures.

  • Noting that thousands of Gt of carbon dioxide would be needed to cause the planet's temperature to rise 5-9°C, the point that is often missed is that it is the absolute level of atmospheric CO2 that is important if one is interested in absolute temperature levels. To make things as hot as the PETM you would need the same level of GHG in the atmosphere as then, regardless of where you start from.

  • Another thing that is often missed is that the GHG released at the start of the PETM was removed from the atmosphere quite rapidly, taking on the order of 20,000-40,000 years. In fact, a recent paper states that the ecosystem accelerated its rate of carbon sequestration in response to the PETM release (see “Rapid carbon sequestration at the termination of the Palaeocene–Eocene Thermal Maximum”). The implication here is that, though a massive release of CO2/CH4 can cause a rise in global temperatures, such a rise is only a perturbation of the system. The system will correct itself over time by removing any “excess” carbon from the atmosphere.

That last point is quite important in that it shows that CO2 does not regulate Earth's climate. Sure, it does have an impact on temperatures, but it cannot cause long-term changes in climate because it is rapidly removed from the environment. To keep temperatures at PETM levels would require an ongoing release of thousands of gigatons of carbon. Other things drive climate with CO2 acting as one of the many feedback mechanisms within the system. Human CO2 emissions may cause some temporary warming but the system is actively working to remove those emissions. For these and other reasons I find the CO2 global warming threat overblown.

See my earlier article, “Could Human CO2 Emissions Cause Another PETM?,” for details and links to papers. For more on what caused the PETM see “Ancient Evidence That CO2 Does Not Control Climate.”