Most dangerous error ?

Is climate sensitivity=3 from the IPCC humanity's most dangerous error?


A single number "3" is the basis for all climate projections and for all climate policy,

including NetZero. (Zero Emissions 2045).

If the number gets even slightly higher, the whole climate policy falls.


If the climate sensitivity turns out to be greater than 3, the NetZero policy cannot offer any

future  for the world. Therefore a discussion on climate sensitivity must start in the press

and in all media.


All politicians and all citizens should think deeply about the implications.

This concerns absolutely everyone

and it may be the most important point in the whole climate work.


The well-known climate scientist Professor Johan Rockström writes:

If climate sensitivity is 4-5 degrees rather than 3 degrees,

then the entire remaining emission space disappears in one fell swoop.

Nor can we stop global warming at 1.5 degrees.


The IPCC has been claiming for 40 years that the climate sensitivity is 3, which means that the Earth's

temperature rises +3C for every doubling of CO2 levels.


The following well-known sign from the IPCC, is a very accurate

mathematical consequence of climate sensitivity 3. This sign has been designed

Bill 2016/17:146 and forms the basis of the Climate Act 2017:720

and the NetZero policy (Zero Emissions 2045).






Professor Svante Arrhenius used basically the same formula (*Ref1)

120 years ago but claimed climate sensitivity=6


Johan Rockström writes: James Hansen, formerly of NASA and one of the world's foremost

climate scientist, showed already more than ten years ago that

climate sensitivity, when including slow feedbacks, ends up being

6 degrees.


Climate sensitivity is a measure of how strongly a planet is warmed by CO2.


The higher the climate sensitivity, the higher the forecast for warming.

If we look at today's situation using Svante Arrhenius' 120 year old logarithmic formula (*Ref1)

we get valuable and interesting conclusions: (The formula is just as relevant today and used by IPCC)


The IPCC has been calculating climate sensitivity 3 for 40 years.

Thought model: the Earth is then in an oven that holds +1.7 C right now (*Ref2)

while the earth itself is +1.1C

We know from NASA that the Earth is currently warming by +0.035 C/year.

If all emissions are stopped today, the Earth will reach +1.7 C in about 17 years. (*Ref3)

After that, global warming stops.

One could argue with good will that 17 years is almost zero.

Then the last report from the IPCC, which claims that the temperature

stops immediately when emissions are stopped. The whole world's climate policy

NetZero rests on this foundation.


If we instead believe James Hansen and count on climate sensitivity 6:

The Earth is then in an oven holding 3.5 C right now (*Ref4)

while the Earth itself is +1.1C

As said, we know from NASA that the Earth is currently warming by +0.035 C/year.

If all emissions are stopped today, the earth will reach +3.5 C in 70 years (*Ref5)

If all emissions are stopped by 2050, as NetZero prescribes, it will only be

far worse than +3.5 C.


6 instead of 3 -- will have huge consequences.

At 6, it is no longer true that the Earth's temperature will stop when emissions are stopped.

Temperatures continue when emissions are stopped.

Then the whole foundation for NetZero (Zero Emissions 2045) falls and it is not in

human power to prevent +3.5 C


Quote Johan Rockström: .... then the entire remaining emission space disappears in one fell swoop.

Nor can we stop global warming at 1.5 degrees.


As I said, it is not in human power to prevent +3.5 C with zero emissions.

Even if the whole world converts to solar, wind and electric cars today

it's not nearly enough.


Much tougher action is needed. Relatively simple maths shows that 200 Gt of CO2

and 2 Gt of methane must be sucked out of the atmosphere every year.

Starting no later than 2025. Then we can meet the Paris Agreement

and at that rate the entire atmosphere will be restored to 18th century atmosphere within 30 years.


Atmospheric methane has 120 times more greenhouse effect than CO2. A side-effect is that if you just

1% of atmospheric methane is added to diesel, the fossil fuel becomes climate neutral. In this way

the world can become climate neutral decades sooner than NetZero policy can offer.

while society doesn't have to be brought to its knees by astronomical fuel prices.

If we continue towards NetZero but miss all the innovative measures, a bottomless misery awaits soon.

If all this is done smartly, we can continue to raise living standards to levels that we cannot

imagine today. Quote Vinod Khosla: We can invent the future we want, as long as the experts don't stop us.


This very likely scenario with climate sensitivity >= 6 needs to be brought up for discussion.

The issue should fill the press and media and be treated as possibly the most important issue in the whole

climate work.


Quote Rockström:

We live in a new risk landscape. A climate sensitivity of 3 degrees is already an enormous challenge. We have to become fossil-free in a generation. But the mere fact that the most sophisticated climate models point to the risk of higher sensitivity calls for reflection, caution and, above all, action.


Action is needed. Climate action may look very different in the future.

A forthcoming article will attempt to address this theme in detail.


Bengt Ovelius




(*Ref1) The formula is 1.443*cs*ln(ppm/275)

(*Ref2) 1.443*3*ln(410/275) =1.7 C

(*Ref3) (1.7-1.1)/0.035 = 17 years

(*Ref4) 1.443*6*ln(410/275) =3.5 C

(*Ref5) (3.5-1.1)/0.035 = 70 years


All quotes from Professor Johan Rockström come from the article

The holy grail, climate sensitivity, is shaken to the core, SVD 2020-07-18



PS The above formulas are linear approximations with the goal to make  

the mathematical understanding is simple. It can be argued that they are over-simplified.

They should only be used to understand the principle. The much more exact values should be

taken from below:


The ordinary differential equation that describes the more precise course for all possible

climate sensitivities looks like this:


Below is the symbolic solution, which is also the engine of our unique climate calculator.

In the calculator you can easily see the dependence of the time constant on the climate sensitivity.

A short user manual is available here.


This seems to be an overlooked area in climate science.

The effect of different climate sensitivities seems to be a crucial area to explore as the entire NetZero

politics depends on it.



There are two outcomes:


1.The above is correct

2.The above is wrong


If it is wrong, it would be a great help if climate experts could provide a correct derivation.


If it is correct, it would be a great help if climate expertise could help and change climate policy

into something that actually works.


It is not a question of the prestige of individuals,

It's about the future of our children.


High climate sensitivity leads to rapid climate change

while a false climate sensitivity=3 from the IPCC provides a false guarantee that

there is no urgency.