Hi Arpad, great question. Very few people understand this yet. The science of this has really only developed since 2000 and a clear understanding of it is still elusive.

I explain this in detail in LiBT-20 but here is a quick precis.

Look at the IPCC chart. See the two red bars and the blue bar. The reason the "Observed Warming" number is lower than the "Well-mixed greenhouse gases" number is the cooling effect that "Other Human Drivers" (the blue bar) is having.

Another name for this is geoengineering. This geoengineering has made it seem cooler than it really should be for a long time.

In this paper "Climate effects of aerosols reduce economic inequality" published in 2020, the lead author states:

"Estimates indicate that aerosol pollution emitted by humans is offsetting about 0.7 degrees Celsius, or about 1.3 degrees Fahrenheit, of the warming due to greenhouse gas emissions. This translates to a 40-year delay in the effects of climate change. Without cooling caused by aerosol emissions, we would have achieved 2010-level global mean temperatures in 1970."

How are we doing this?

Mostly by injecting massive amounts of sulfur dioxide into the atmosphere all around the planet via the diesel fuel used in the world's shipping and military fleets. This cools the planet by making it more reflective to the sun's energy. It increases the Earth's albedo.

The important thing to remember is.

If we stop putting sulfur dioxide into the atmosphere, ALL the cooling effect goes away in 3–5 years.

The estimates for this "masked warming" range from 0.4C to 0.9C.

Now, Hansen thinks that we are about to have a massive surge of warming on top of the El Nino warming. I agree with him.

Because, in January 2020 the the International Maritime Organization (IMO) started the entry-into-force date of a global 0.5% sulfur cap.

Cleaner Air in 2020: 0.5% sulfur cap for ships enters into force worldwide

From January 2020, the maximum sulphur content of marine fuels is reduced to 0.5% (down from 3.5%) globally — reducing air pollution and protecting health and the environment. Sulphur Oxide (SOx) emissions from ships’ combustion engines cause acid rain and generate fine dust that can lead to respiratory and cardiovascular diseases, as well as reduced life expectancy.

The shipping industry is among the world’s largest emitters of sulfur behind the energy industry, with the sulfur dioxide (SOx) content in heavy fuel oil up to 3,500 times higher than the latest European diesel standards for vehicles.

“One large vessel in one day can emit more sulfur dioxide than all the new cars that come onto the world’s roads in a year.”

That was three years ago. SOx levels in the atmosphere have to be falling as a result of this. We are definitely going to have a very hot couple of years as some of that masked heat catches up with us.

Here's another article I wrote about how this same effect played out in the 30's and helped create the Dust Bowl.

LiBT-13 Anthropogenic Particulate is a form of Geoengineering