Global warming in the pipeline by James E.Hansen: 1.71°C in 2030

James Hansen is one of the world's leading climatologists. He alerted the United States government to global warming. In this video , today's greatest climatologists testify to the excellence of these climate forecasts. He also has enormous experience in the field. I also find his scientific work on sea level rise published in 2016 (article ) very convincing, several of his conclusions and postulates have been confirmed in recent years.

He's been fighting for the climate for decades, and was arrested for climate protests in front of the White House. He has extensive knowledge of climatology. So I really hesitate to contradict him but I have some objections. His work obviously provides many useful elements, and it has the merit of being available today. Given the climate situation, we cannot wait for the next IPCC report.

1. Geophysical models

The study “Global Warming in Perspective ” constitutes an excellent introduction to climatology. It explains several factors that influence the climate. It was published on November 2nd in the Oxford Climate Change Journal. Another text was published on November 9th, and on November 10th he posted a similar communication .

Climate models are based on geological data. Climate is influenced by the concentration of gases in the atmosphere, by exposure to sunlight modified by the Earth's orbit, and by the Earth's surface covered in ice.

Ancient air is still contained in the air bubbles of polar ice. We thus know the atmosphere of past eras. The temperature of the oceans and air is revealed by the shells of tiny marine animals, foraminifera, which are deposited on the ocean floor.

James establishes the effect of carbon dioxide by comparing its concentration and temperatures at various times and obtains a climate sensitivity value. This figure corresponds to the degrees of warming following a doubling of gas in the atmosphere (from 270 to 540 ppm). The IPCC value is around 3°C per doubling of CO2, while this work yields a higher value of 4.8°C. The current concentration of carbon dioxide would therefore already lead to a warming of around 2.5 degrees, in more than a hundred years. Another recent study suggests that the continuation of current carbon emissions would already lead to the triggering of positive climate feedback loops (link ).

Geology is not an exact science. Paleontology has already reconstructed false animal skeletons, creating monstrous beasts. Geology is also fallible. The fossil foraminifera contained in the rock fragment travelled in the ancient ocean, and then the rock formed from them moved too. In addition, a thin geological layer covers a period of a thousand years. Reconstructions of Earth's past likely contain inaccuracies.

2. Aerosols and forest fires

On the other hand, the assertion that the difference between geological data and current reality is due to aerosols seems little justified. James Hansen assumes that humans have always burned a large proportion of plant matter, whereas the IPCC assumes that our burning activities were initially low and then peaked between 1900 and 1950. The difference in the two models can be seen in the graph below. The IPCC curve (IPCC) in dark blue shows that there were few aerosols before 1800, while on that of James Hansen, lighter, they are already high.

On this specific point, I am more convinced by the IPCC version because our deforestation activities, particularly in the Americas, reached a massive scale in the 19th and 20th centuries. I remember a study of smoke around Brazilian airports which indicated a lot of forest fires in the 1960s, another indicates massive deforestation of the Amazon, the Congo forest, and South Asia. Southeast between 1950 and 2009. The scale that this phenomenon reached in the 21st century led to the loss of half of tropical forests. It is certainly unparalleled in history, if we had burned so much forest before, they would no longer be there. Europe, very small anyway, engaged in deforestation in the Middle Ages and North America between the 16th and 19th centuries, more slowly and on a smaller scale. In addition, recent hot years have brought very significant forest fires, in Australia in 2020, in Brazil under the Bolsonaro government, and in Canada in summer 2023. Yet, wood ashes might not have the same effect as fossil fuel residues, while the sulfur components strongly filter solar radiation. Trees emit compounds that promote cloud condensation, I wonder if they did they contribute to the set of aerosols before deforestation.

James attributes the recent escalation in temperatures to the reduction in the use of sulfur fuels in maritime transport. However, he notes that their reduction between 2005 and 2015 did not cause an acceleration in warming, and believes that stricter regulations on maritime fuels put in place in 2015 are responsible.

However, other important phenomena occurred at this time: one of them was the reduction in the ice surface around Antarctica during the Southern summer. This ice reflected sunlight and its albedo cooled the Planet. It suddenly decreased in 2016, and it is an important factor in warming. I asked Sam Carana how much it influenced Earth temperature. According to them, in January 2019 the Earth absorbed 1.6 W/m2 due to the greenhouse effect caused by carbon emissions, and a comparable energy, 1.3W /m2 additional due to the crumbling of the ice pack. Antarctic sea ice reached a new minimum this year, so it may have caused a rise in temperatures. Yet James Hansen might have a better estimation of its importance from NASA.

In recent years, tropical forests have virtually stopped capturing carbon. In particular, the 2015 drought in the Amazon caused a halt in forest growth, the death of trees and the release of CO2 from trees and the soil. Natural carbon sinks, forests and grasslands, accelerated their growth when C02 increased in the atmosphere in the 20th century, but their functioning is now undermined by droughts. Global methane emissions have increased, likely coming from swamps.

Another new factor mentioned by Paul Beckwith is the increasing stratification of the oceans which reduces the absorption of heat and CO2. A greater proportion of carbon dioxide and of solar energy remains in the atmosphere. These hypotheses could be verified by comparing atmospheric CO2 with energy and temperature.

In another communication, James Hansen spoke about the effect of aerosols and clouds. We have little indication of past clouds, which have a very strong effect on solar radiation reaching the planet. Paleobotany perhaps provides an answer. Overall, I find that the importance of aerosols for the climate of past centuries and for that of recent years is uncertain. I also wonder if the notion of climatic sensitivity, established for thousands of years, is adapted to the scale of a human life. The biosphere was able to withstand the first changes, then, once its resistance begins, the following ones will have spectacular effects for us.

3. Solar energy absorbed by the Earth

Current warming is confirmed by two other measurements independent of geology: measurements of global temperature and of solar energy absorbed by the Earth in recent years. The driver of global temperature change is Earth's energy imbalance (EEI). This is the difference between the energy that the Earth receives from the Sun and that which is reflected and radiated towards space. We now have a good measure of EEI. It is obtained by precise measurements of the radiation reflected and emitted by the CERES satellite. As long as this imbalance remains positive – more energy coming in than going out – the Earth will continue to warm (Hansen, communication November 10, 2023). And as you see in the figure below, the energy imbalance is positive and increasing.

Ten years ago, James estimated the EEI during the first decade of this century to be +0.6 W/m2 on average across the planet, which is about 16 times greater than the total energy consumption of the planet. humanity and equal to the energy of 400,000 Hiroshima atomic bombs. per day. Since then, fossil fuel emissions have increased and Earth's energy imbalance has nearly doubled. About 90% of this excess energy is slowly warming the ocean. This indicates that temperatures will rise over the next few years.

4. Recent temperatures

The graph below shows the increase in Earth's temperature. El Nino years are always warmer, they are visible as small peaks on the graph. Between 1970 and 2010 warming was 0.18°C per decade, then it reached 0.24°C between the two super El Ninos of 1997-98 and 2015-2016 . Now James Hansen estimates warming at 0.27°C per decade.

Over the past two months, in September and October, the Earth's temperatures have undergone a very significant increase, and James emphasizes that this is not a coincidence, but the effect of the significant excess of energy accumulated by the Planet. Warming is understood and expected. The graphic published in the November 10th communication contains a fuchsia dot added to that of the publication. This is the expected value for this winter's El Nino. Indeed, in recent weeks official press releases have confirmed that we are entering a phase of strong El Nino, which will cause global temperatures to rise over the coming months. The World Meteorological Organization announced last week that El Nino has taken hold, will last until at least April 2024, and will likely cause an increase in global temperatures. WMO chief says next year 2024 could even be warmer. This point is enough to show us that James' predictions are very reasonable.

5. Conclusions

The solar energy absorbed by the Earth has doubled since 2006, and the temperature is increasing faster. These two facts are certain and very alarming.

Hansen's calculations show that over the next decade we can expect a temperature increase of 0.4°C, which would lead us to warming of 1.71°C in 2030 and 2°C in 2040. They are based on the geophysical model and climate sensitivity it established, but we see how warming is progressing quickly and several elements of the Earth system appear to be contributing to an acceleration.

The threshold of 1.5°C on a ten-year average was set in the Paris Agreement in order to avoid a total disruption of the earth's climate; if we exceed it, many dangerous phenomena could be set in motion, disasters would affect entire cities, and the change would then amplify.

In 2017, James Hansen wrote that it was still just possible to avoid a significant rise in sea levels, by quickly phasing out fossil fuels, improving forestry and agricultural practices, and reducing emissions. of methane. Today, in 2023, he considers it's too late. If carbon emissions continue according to current rules, global warming will exceed 1.5°C in the 2020s and 2°C before 2050. Weather impacts on populations and nature will accelerate. He therefore states that the enormity of the consequences demands a return to Holocene global temperatures, which would require: (1) a global increase in the price of GHG emissions accompanied by the development of clean energy, (2) cooperation adapted to the needs of developing countries, and (3) intervention on terrestrial radiation, probably by geoengineering SRM (solar radiation management), i.e. dispersion of aerosols, or by projection of droplets of ocean water to form clear clouds (cloud brightening).

?James also suggests cooperation between the United States and China for the development of “low-cost nuclear power”. I rather propose cooperation for the production of useful, long-lasting, repairable goods, as Club of Rome suggested. Such a change would reduce energy consumption. In addition, it would be compatible with safeguarding biodiversity. It appears more and more that it is essential for our survival on Earth, the Secretary-General of the UN declared last week that without Nature, we have nothing.

I am convinced by the acceleration of warming but not by the importance of aerosols. It's deduced from volcanoes. When they propel plumes of ash and gas into the atmosphere, the weather gets generally colder and rainier. The effect of industrial aerosols should, however, be confirmed by measurements as quickly as possible. I think the acceleration may be caused by other factors, such as shrinking sea ice around Antarctica, damage to natural carbon sinks like rainforests, and increasing ocean stratification.

? All these modifications to the Earth system contribute to more rapid climate change, and above all terrestrial CO2 emissions are still extremely high. Temperature measurements indicate an acceleration of global warming. James Hansen had already established this in many ways, comparing La Nina years, El Nino years and now the temperature between decades,? measure also used by the IPCC.

It's extremely worrisome. We know the situation is serious. However, James' predictions are made based on current carbon emissions. We can turn the tide by urgently reducing carbon emissions this year and the next five years, for example by reducing aircraft flights or plastic factory activity and immediately increasing carbon capture. carbon from plants. The IEA also calls for immediate control of methane emissions.

Recent articles:

Global warming in the pipeline: Warming in perspective, November 2, 2023: https://academic.oup.com/oocc/article/3/1/kgad008/7335889?searchresult=1

? How we know that global warming is accelerating and that the goal of Paris agreement is dead, November 10, 2023 https://mailchi.mp /caa/how-we-know-that-global-warming-is-accelerating-and-that-the-goal-of-the-paris-agreement-is-dead

A recent review on aerosols if you want to solve this issue: Aerosols

Translation of my blog on the global-climat website: https://global-climat.com/2023/11/14/rechauffement-climatique-en-perspective-selon-james-e-hansen-1-71c-en-2030/

Addendum: a recent publication shows that aerosols trigger cloud formation and cool the Planet https://www.science.org/doi/full/10.1126/sciadv.adh7716 but that doesn't explain past centuries temperatures in James's model. Forests were bigger and emitted some more aerosols..