CO₂ coalition sponsored article in The Washington Times presents list of false and misleading statements about the impacts of CO₂ and climate change

“The science and data strongly support that our planet’s ecosystems are thriving and that humanity is benefiting from modestly increasing temperature and an increase in carbon dioxide.” ; “Earth’s ecosystems and inhabitants are thriving because of increasing CO₂ and rising temperatures not in spite of them.”

Wolfgang Cramer, Professor, Directeur de Recherche, Mediterranean Institute for Biodiversity and Ecology (IMBE):
There is no science nor is there any data that globally support the assertion that ecosystems are thriving or that humanity would benefit from increasing temperature or increasing carbon dioxide. There are literally tens of thousands scientific publications that indicate that ecosystems are increasingly being degraded due to climate change and other impacts^[1-4]. Many people have lost their lives during heat waves or climate change caused natural disasters^[5,6].

Alexis Berg, Associate Research Scholar, Princeton University:
It’s true that vegetation has been increasing globally in the last 40 years (since we have satellite measurements). Models suggest CO₂ fertilization is the main contributor to the growth of forests and natural ecosystems^[15]. Warming has beneficial effects in high-latitude, temperature-limited regions (e.g., Arctic greening), but opposite in the Tropics. Direct human management (agriculture, afforestation) also plays a role in some regions^[15].

However, further warming could start having more negative effects on global vegetation, while the beneficial impacts of CO₂ could run into some limitations (e.g., nitrogen limitation)^[16].

Note as well that current warming levels already have very noticeable negative impacts on marine ecosystems (i.e., coral reefs)^[1-3].

“These facts refute the claim that Earth is spiraling into one man-made climate catastrophe after another.”

Wolfgang Cramer, Professor, Directeur de Recherche, Mediterranean Institute for Biodiversity and Ecology (IMBE):
There is no claim of any „spiraling“, there is just a very robust assessment that greenhouse gas concentrations are rising, that they cause rapid climate change, and that the societal consequences of these changes (economy, health, etc.) will be disastrous for a large part of the world’s human population in the near future^[4-7].

“Concentrations of this gas are slightly less than 420 parts-per-million (ppm), or one-sixth the average historic levels of 2,600 ppm for the last 600 million years”

Wolfgang Cramer, Professor, Directeur de Recherche, Mediterranean Institute for Biodiversity and Ecology (IMBE):
To compare with the last 600 million year average is irrelevant. Levels are unprecedented with respect to the time that humans have lived on Earth.

Katrin Meissner, Professor, University of New South Wales:
This statement is partially correct. The average historic level was not 2600 ppm, but there were periods of times when CO₂ was very high, likely as high as 1500-2000ppm. The ecosystems and biogeochemistry were adapted to these conditions, and they looked very different from today. There were no humans, many of the mammals around us did not exist. Not to mention that the sun’s energy output was slightly smaller during that time. Changing the present day world into a “dinosaur world” within a century would not be good news for the ecosystems we depend on, or for us.

Alexis Berg, Associate Research Scholar, Princeton University:
This is a silly point. Yes it was hotter, with more CO₂, hundreds of millions of years ago, but humans – mammals! – weren’t there. We care about change now. 420ppm is unprecedented in the last million years at least. By the same token one could say that during the last 600 million years the Earth was mostly ice-free (no ice caps) – so we shouldn’t care if the ice caps melt now (i.e., 70 m of sea-level rise).

“Increases in carbon dioxide in the last 150 years, largely from the burning of fossil fuels, have reversed a dangerous downward trend in the gas’ concentration. During the last glacial period, concentrations nearly reached the “line of death” at 150 parts per million, below which plants die. Viewed in the long-term geologic context, we are actually CO₂ impoverished.”

Katrin Meissner, Professor, University of New South Wales:
Plants have adapted to lower CO₂ concentrations, for example with the appearance of C4 plants. Also, the CO₂ concentrations have varied between similar minima during glacials and maxima during interglacials over the past 800,000 years. All the minima are well above 150 ppm.

Alexis Berg, Associate Research Scholar, Princeton University:
The last part is not untrue, but irrelevant. Pre-industrial (around 1800) CO₂ was 280ppm. For the last 10,000 years (human civilization) it has been around that value, increasing slightly – not decreasing – until modern emissions began. Even without current CO₂ emissions and associated warming, there would be no threat of imminent ice age or very low CO₂ conditions.

“The first 250 years of that warming preceded 20th century CO₂ increases and were necessarily 100% naturally driven.”

Wolfgang Cramer, Professor, Directeur de Recherche, Mediterranean Institute for Biodiversity and Ecology (IMBE):
The author makes the frequent mistake of mixing natural variability (the slight warming after the Little Ice Age) and current warming, which is due to greenhouse gas forcing^[17]. These processes are well understood by climate scientists. In fact there is no alternative explanation for the recent rapid warming, as described in this Climate Feedback review.

“Longer-term data reveal multiple warming periods since the end of the last major ice age 10,000 years ago, each warmer than today.”

Alexis Berg, Associate Research Scholar, Princeton University:
Following the last ice age (20 thousand years) and deglaciation, current (Holocene) global CO₂ and climate conditions were reached around 10 thousand years ago. Global temperatures kept slightly increasing until the Holocene maximum, around 7 thousand years ago, and then slowly decreased, until the abrupt warming of the last 150 years. The recent reconstruction by Kaufman et al. (2020) indicates that „The warmest 200-year-long interval took place around 6500 years ago when global temperature was 0.7 °C (0.3, 1.8) warmer than the 19th Century (median, 5th, 95th percentiles).“

Whether or not we are already there, the fact is that modern warming is going to lead to global climate conditions several times warmer than that (e.g., if we get to +3 or 4°C of global warming).

Figure 1—Global mean temperature of the last 12,000 years using different methods to reconstruct past global mean surface temperature (colored lines). The black line indicates instrumental data from 1900-2010. From Kaufman et al (2020)^[18].

“There is a strong correlation between the rise and fall of temperature and the ebb and flow of civilizations. During the last three warm periods dating back 6,000 years to the advent of the first great civilizations, humanity prospered and great empires arose. Intervening cold periods brought crop failure, famine, and mass depopulation. History advises us to welcome warmth and fear cold.”

Katrin Kleemann, Science Editor, Climate Feedback:
The examples mentioned here are vague, it is unclear which cold periods or which incidents of crop failure, famine, or population loss the author refers to. It is also unclear which “civilizations” the author is referring to.

While it is true that past societies experienced natural climate change, these were regional and smaller in magnitude than present-day global warming. Nevertheless, the climate change during periods, such as the Late Antique Little Ice Age or the Little Ice Age, was profound enough to alter human life. It is, of course, deterministic to argue that the climate was the only factor that brought about crop failure, famine, or population loss. In reality, several factors come together that can then lead to crop failure or famine: for instance, inadequate planning, social upheaval, economic struggles, conflicts with other groups, etc.^[19].

Past scholarship has focused a lot on the collapse of societies; however, recent scholarship has discovered that past societies and communities often were resilient in the face of modest climate change. Despite the climatic change, these societies or communities maintained their structure, function, and identity. Some societies adapted to the new, often colder, climatic regime and even managed to exploit the opportunities created by the shift in environmental circumstances^[19].

The climate change faced by societies during the Late Antique Little Ice Age or the Little Ice Age was modest compared to the much greater magnitude of climate change that we are facing in the present and future due to the warming that our greenhouse gas emissions are causing. In the present, we are already experiencing what it looks like to live in a warming world – heat waves, rising temperatures on land and in the oceans, wildfires, to mention but a few, have devastating consequences for millions of people around the planet^[19].

Wolfgang Cramer, Professor, Directeur de Recherche, Mediterranean Institute for Biodiversity and Ecology (IMBE):
There is no such „strong correlation“. The rise and fall of social systems is affected by many factors and climate may be one of them. In most cases, there is insufficient evidence to explain the fall of past societies with a single factor. More importantly, none of the past „civilizations“ had similarly large global populations and similarly high dependence on stable environmental conditions.

Heat waves are becoming more frequent and more severe in many parts of the world. They even occur in the ocean and are one of the key drivers for the loss of tropical coral reefs.

“Modestly warming temperature and increasing carbon dioxide lead to longer growing seasons and more productive harvests. The world’s remarkable ability to increase food production year after year is attributable to mechanization, agricultural innovation, CO₂ fertilization, and warmer weather. Crop and food production has seen only positive effects from relatively small changes in the global climate.”

Katrin Meissner, Professor, University of New South Wales:
Plants cannot live on CO₂ alone. Those plants that profit from higher CO₂ will need more water to maintain their larger growth and to compensate for larger evaporators-transpiration due to increased heat. They will therefore be more vulnerable to changes in precipitation patterns, and to aridification, which will be one of the consequences of higher CO₂ levels in many regions^[20]. They will also need more nutrients, which are not necessarily available^[21,22]. Other plants do not profit from higher CO₂, and their photosynthesis rates have been shown to decrease under higher CO₂. More importantly, higher CO₂ has been shown to reduce the nutritional quality of some plants we depend on, such as wheat^[14].

Sara Vicca, Postdoctoral research fellow, University of Antwerp:
Modestly warming temperature indeed leads to longer growing seasons and modest warming and increasing carbon dioxide can lead to more productive harvests (depending on the local conditions). However, with global warming, heatwaves and droughts are increasing in frequency and intensity^[20]. Increases in extreme weather events can have strong negative effects on crop productivity and are expected to negatively impact food production^[23].
Crop and food production as well as human settlements are also threatened by the increasing risk of wildfires due to global warming.

Alexis Berg, Associate Research Scholar, Princeton University:
It is complicated to separate all factors contributing to crop yield changes, but there is evidence suggesting that global warming is already negatively impacting global food production, at least in some regions^[24]. Note that crop yields respond not only to mean climate, but also to extreme events (e.g., heat waves, droughts) that get more intense and/or frequent with warming^[23]. Of course, further warming makes it only more likely that negative impacts will start occurring.

“Contrary to sensational media reports, extreme weather-related deaths in the U.S. have decreased more than 98% over the last 100 years. Twenty times as many people die from cold as from heat, according to a worldwide review of 74 million temperature-related deaths by Dr. Antonio Gasparrini and a team of physicians. Global warming saves lives.”

Antonio Gasparrini, Senior Lecturer, London School of Hygiene and Tropical Medicine:
I think Mr. Wrightstone refers to an article I published some time ago, where we showed that indeed cold is currently associated with a much higher mortality^[5].

However, this does not mean that the decrease in cold-related deaths expected with the warming of the planet will offset the heat-related increase in the future. Actually, from the evidence we have gathered so far by a follow-up study on an even larger dataset , it seems that this is not true unless in mild warming scenarios that require strict mitigation strategies^[6].

Katrin Meissner, Professor, University of New South Wales:
This statement is false, based on fatality data from NOAA.

Alexis Berg, Associate Research Scholar, Princeton University:
Moot point. The concern about global warming doesn’t stem from the direct impact of atmospheric conditions on human lives or deaths, but rather from its impact on the environmental factors that support society – water resources, natural and cultivated ecosystems, ecosystem services, etc. Note, however, that an increase in humid heat could lead to literally lethal atmospheric conditions during heatwaves in parts of the Tropics under a high-warming scenario.

“During this period of increasing CO₂ and slight warming, we have seen increasing food production, soil moisture, crop growth, and a “greening” of the Earth. All the while droughts, forest fires, heat waves, and temperature-related deaths have declined substantially.”

Wolfgang Cramer, Professor, Directeur de Recherche, Mediterranean Institute for Biodiversity and Ecology (IMBE):
Unfortunately, droughts, forest fires and heat waves are increasing world-wide, and so do temperature-related deaths^[6,25]. The statements made here are invented by the author and entirely „at odds with reality“.

Sara Vicca, Postdoctoral research fellow, University of Antwerp:
The earth has indeed been greening in the past decades, and this has been attributed primarily to the increasing CO₂ concentrations^[26]. Terrestrial ecosystems have sequestered about 30% of anthropogenic CO₂ emissions, and this land sink has retarded climate change^[27]. However, as global warming progresses, negative impacts of especially heat and drought are increasing. In fact, we are already seeing the first signs of a decline in the land CO₂ sink and increasing extreme heatwaves and droughts seem to be the most important reason^[16,28,29].

Katrin Meissner, Professor, University of New South Wales:
Droughts and aridification have increased in many regions of the world. For example in Europe and North America^[30,31]. Forest fires have increased and now show the fingerprint of global warming, e.g. in Australia^[32] and the Arctic. Heat waves have increased in frequency, intensity and duration^[33].

Alexis Berg, Associate Research Scholar, Princeton University:
I am not aware of any study showing an increase in soil moisture over the last decades (soil moisture is exceedingly difficult to measure globally). Heat waves have demonstrably increased^[34]. Global burnt area has decreased globally over the last 20 years, yes (by 25%), but that signal is dominated by agricultural intensification and expansion, which replaces naturally-burning grasslands and savannah, in particular in the Tropics^[35]. Some regions clearly show warming-influenced growth in wildfires in natural ecosystems (e.g., Western US, high latitudes).

Changes in drought frequency/intensity are complex and hard to estimate – warming may not cause more droughts but may make existing ones worse. But in any case, the consensus is certainly not that there has been any „substantial decline“ in droughts in recent decades.

“Yes, there has been some warming, but it has been minuscule compared to the temperature change all of us experience in the course of a day.”

Katrin Meissner, Professor, University of New South Wales:
The overall global warming that has been observed so far is small compared to the diurnal temperature difference we experience every day. But this is also a meaningless statement.

We could take our daily food intake as an example. Most of the minutes of the day we eat nothing. During dinner, we might eat a pizza and drink a beer and therefore absorb 2000 calories within 20 minutes. Our intake throughout the day varies between 0 and 1000 calories per 10 minutes, assuming that our breakfast and lunch is a bit less calorific. Compared to a range between 0 and 1000, 10 calories is nothing – I therefore suggest we should all constantly eat 10 calories every 10 minutes throughout the day, on top of our normal intake, and let’s see what this will do to our health.

UPDATES:

• 9 June 2021: Two of Amber Kerr’s statements were updated to explain that current global average temperatures are some of the highest since before the last Ice Age and to clarify the results discussed from Burke et al. (2018)^[10].

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