Paul Mauritz Glantz Researcher

I defended my thesis in 2002, which includes studies about aerosol-cloud interaction in the marine boundary layer based on in-situ aircraft measurements. Thereafter, I continued to investigate atmospheric aerosols based on satellite observations (see publication list). At present, however, the turn-over point of the aerosol era and corresponding reduced cooling effect, in addition to all times record in carbon dioxide in the atmosphere with the highest level within a period of 3 million of years, suggest that focus should be on the rapid warming observed globally. This mean also immediately actions to reduce emissions of greenhouse gases globally.      

 

Why we more than ever need to rapidly reduce the emissions of greenhouse gases to save the climate

The indirect aerosol effect (cloud albedo effect) is associated with the largest uncertainties in radiative forcing among the climate drivers, presented in the latest IPCC report AR6. At present, human aerosols are masking greenhouse warming in Asia, particularly in Eastern China and India. AR6 gives a potential global mean negative radiative forcing of 1 W m-2, which means about 0,5 degrees potential masking effect of the atmospheric aerosols, although the estimate is associated with large uncertainty.            

The global mean radiative forcing of the aerosols has been nearly unchanged after 1980, while the global mean net radiative forcing (positive) has increased substantially during the same period, particularly due to increases in anthropogenic carbon dioxide. During the same period anthropogenic aerosols have decreased substantially in Europe after 1980, which means that the aerosol’s masking effect on greenhouse warming is more or less history. This is also the case for other regions on Earth where aerosols have decreased substantially. In the Glantz et al. (2022) study we found that warming in Europe in the summer half year since 1980 is about double the increase in global mean temperature of 1,1 – 1,2, since the beginning of the industrial revolution. Our results are in line with WMO who found that the warming goes fastest in Europe among the continents. In addition, warming over global land areas is 1,6 degrees during the industrial era, which can be compared to 0,9 degrees over the oceans (IPCC, AR6).

Decreases in aerosols and consequently increases in solar radiation downward near the surface means amplification of the greenhouse effect, which in turn results in more energy absorbed by the Earth surface. In the Glantz et al. (2020) study we find that the land surfaces in Europe, particularly in the southern part and France, has dried out during the latest four decades. This results in a shift to sensible heat flux at the expense of latent heat flux, which in turn has led to additional warming of the lower atmosphere at the same time as evaporative cooling has been reduced.  

The global warming results in more water vapour in the troposphere. The relative humidity has however decreased over land, which makes it harder to cross the vapor-liquid phase. The greenhouse effect caused by increases in water vapour is thus even more efficient today due to less amount of clouds presented. The latter means increases in solar radiation toward the surface. Together with an additional enhanced greenhouse effect, caused by higher levels of water vapour in the atmosphere, more energy is available at present day to warm up the lower atmosphere. The humidity paradox, increase in water vapour and decrease in relative humidity, is a result of increases in solar radiation and enhanced greenhouse effect, particularly by anthropogenic carbon dioxide. This has initiated the positive feedbacks described above that highly contribute to the extreme warming observed globally above land. Furthermore, many monthly global heat records were broken in 2023, particularly above land during autumn in the northern hemisphere. 2023 was 0.60°C warmer than the 1991-2020 average and 1.48°C warmer than the 1850-1900 pre-industrial level, which means

close to the Paris agreement of 1.5°C.

The end of La Niña and start of El Niño during this year have likely contributed to the temperature record in 2023.