This is not a high quality paper, it's riddled with errors. It should never have been on mainstream news or on TV. Those 11,000 scientists are not authors - they are just signatories and one of them is the illustrious professor Micky Mouse of the Micky Mouse Institute of the Blind in Namibia. Of course they removed those names once they were discovered, but this shows how easy it was to add signatures to it.

Climate change is a serious issue but it does no good to promote things like this as if they were on a par with the IPCC reports.

The only section number cite to the IPCC is mistaken, says that it says we need carbon taxes much higher than $15.25 - the actual figure in that section for an example carbon tax together with other measures is $7.

Their only cite for the tipping points is a schematic vague concept study that labels its figures with "hot" and "cold", doesn't give figures for"hot" or "cold", and just has an axis for "Time" not labeled with centuries or millennia.

Their only cite on population perpetuates the myth that we can solve population problems in third world countries by flooding them with family planning and contraceptives!

The basic problem here is high child mortality in third world countries, including children dying of diarhea and easily cured diseaes. They need to have many children so that some reach adulthood and look after their smallholding, Contraceptives can't help their children to grow up safe and healthy! That has to be high priority, as well as education and opportunities for women. None of this is mentioned anywhere in the paper or the paper they cite. I go into this in detail below.

I don't know how they got 11,000 scientists to sign it, but the Micky Mouse thing shows that even pranksters could sign it and they didn't notice. If the IPCC reports could be signed they'd probably have hundreds of thousands of signatures.

Micky Mouse has now been removed. Along with Albus Dumbledore apparently.

Many of the signatures are from professors of agriculture, forestry, astrophysics, mathematics, almost any discipline except climate scientists. Out of those 11,000 names, only 190 have the word climate or climatology in their profession.

There is nobody there from the IPCC bureau, and as I go through the paper you’ll begin to understand why

This is NOT a systematic review by climate scientists like the IPCC, it's just a paper in the form of a letter and those 11,000 people are signatories, not reviewers or co-authors. They have nothing to do with writing it, weren't reviewers, and haven’t commented on it or corrected it. All they did is sign it.

The study itself is here: (Ripple et al., 2019, World Scientists’ Warning of a Climate Emergency)

The language is vague and imprecise, e.g. “uninhabitable” is not defined and not cited to any other source that defines it. If you think the term is clear, have a try at defining it yourself right now, before we get to a detailed discussion of it.

It has only one section number cite to the IPCC. It says a carbon tax “much higher” than $15.25 is needed.

The actual example figure for a carbon tax in that section is $7 (when combined with a ban on new coal-based power plants and dedicated policies for renewables and electric vehicles). The higher "carbon prices" given in that section are not intended for use as carbon taxes, and the section explains the distinction (I go into this in detail below).

Its other IPCC cites are to complete reports instead of by section number making it impossible to know which section they are meant to refer to if any.

Another claim in the paper, which is also uncited, is that global warming threatens the fate of humanity:

The rightmost drawing here with all the ice melted is not 2100, it's the year 3000, and that is for constant emissions at current levels through to 2300 - the extended "Business as Usual"

Did none of them check the cites? Or if they did, and know they were mistaken, why sign it?

Those are just a selection. Here are some of the others who ran it "as is". Independent, Washington Post, CBS News. India Today. BBC, Guardian. USA Today, CNN World, Bloomberg, Boston Globe, Smithsonian Magazine, Popular Mechanics, Popular Science, The Hill, Economic Times

Compare this with the IPCC reports which are worked on by hundreds of scientists, every sentence cited, with error margins with lots of details and run to hundreds of pages.

No the IPCC does not err on the side of least drama, just follows scientific method

This one is less than 3000 words and at a typical college level reading speed of 300 wpm you can finish it in ten minutes. It doesn’t have any complex arguments and has few cites. Most signatories have probably read the paper and perhaps some of the cites - though there is no check that they did.

Their only tipping point cite is the paper Trajectories of the Earth System in the Anthropocene. This is is one of the figures in it:

There are no measurement units either here or in any of the figures in this paper they cite and it doesn't discuss timescales in the text either, or how hot "hot" is or how cold "cold" is. That wasn't their objective, and the paper doesn't attempt to clarify this. The authors of this cite themselves say it is about a “possibility” not a “probability” and there were other scientists who were skeptical about its findings.

This is no substitute for the detailed projections reviewed by the IPCC. It is not trying to do the same thing, and is mainly about possibilities that could unfold on unspecified timescales of millennia, like the melting of ice sheets, or centuries like the slow thawing of the permafrost in Arctic regions (a significant amount of the permafrost thaws over the first century but it takes many centuries for it to reach equilibrium).

If that surprises you - and many people have got the impression from the mainstream media that these events would unfold rapidly, see:

For population they cite a single controversial paper from 2018.

These cites are nowhere near substantial enough for such a radical change of projection and change of policy.

I think most people who share it, sign it, and journalists who write the stories are so used to those ideas from the mistakes in the mainstream media they probably don't even realize they are saying something radically different from the IPCC.

The 11,000 scientists didn't work on this report. They can't have checked the cites. Either that or they are willing to sign a paper that misrepresents its cites and that comes to radically different conclusions from the IPCC reports on the basis of two controversial cites. I.e. they were. signing it not as an endorsement of its conclusions or as an indication that they have fact checked it themselves, but as a call for action.

The IPCC by comparison is a collaborative effort of hundreds of scientists. Moreover the IPCC reports are systematic reviews - a technique developed from medicine where it is of course very important to get accurate information. For details of the background as applied in medicine, see: Medical research: Systematic review and meta-analysis

For more about this see my:

This is not a systematic review. With its two major points of divergence from the IPCC each based on a single controversial paper, it is not a review of the literature at all.

It is just one paper that picks a few papers to support its ideas. It is only written by its authors.

There is no comparison.

The reason I wrote this is because this story is scaring people I help, who read it and think it means there is a risk of billions dying in a largely uninhabitable world too hot for humans, which is not what the IPCC says. The IPCC gave an example worst case in their 2018 report which may be worth looking it if you have come to believe they said that. It's Box 8 of chapter 3 of the 2018 IPCC report. I discuss it here:

The IPCC’s own worst case climate change example - a 3°C rise by 2100

This is another article I'm writing to support people we help in the Facebook Doomsday Debunked group, that find us because they get scared, sometimes to the point of feeling suicidal about it, by such stories.

Do share this with your friends if you find it useful, as they may be panicking too.

Here is a video where I talk about this blog post if you prefer to listen to someone talking:

(click to watch on Youtube)


The problem here isn't them saying we need to increase the pledges - yes of course we do - the Paris agreement was set up with that as how it works.

I expect most of the signatories did it because they agreed on the need for urgent action. That’s not controversial at all.

But the controversial thing, which hit the headlines around the world, is that they say we have tipping points that could lead to parts of the world being uninhabitable, which is not what the IPCC say.

They also say we need to stop population growth urgently which is not what the IPCC say either.

Those are radical changes from the results of the IPCC high level systematic reviews. To support this major change in projections, and suggestions for the most effective policy, they have those two controversial papers, as their only cites.

The most remarkable finding I think is how many scientists signed it without checking its cites. Also how many media stories ran about it too, with none of those journalists checking the cites either, at least, they don’t mention the carbon tax mistake or the uncited "uninhabitable" or any of these other issues.


Most of the cites to the IPCC are vague statements with no precise scientific meaning.

An immense increase of scale in endeavors to conserve our biosphere is needed to avoid untold suffering due to the climate crisis

What does "untold suffering" mean to a scientist?

but the global emissions-weighted average price per tonne of carbon dioxide was only around US$15.25... A much higher carbon fee price is needed (IPCC 2018, section

What do they mean by "much higher"?

The section they cite there says a tax of $7 is appropriate mixed with other policies and that even a carbon tax of $100 per ton is not as good as setting stringent minimum performance standards.

With such vague words as “much higher” it’s not possible to know for sure which of the many figures they are referring to in that section, but they probably were making the same mistake the NY Times did in 2018 their article where they confused the carbon price in that section with the carbon taxes incentives.

For instance, the report says that heavy taxes or prices on carbon dioxide emissions — perhaps as high as $27,000 per ton by 2100 — would be required.

Major Climate Report Describes a Strong Risk of Crisis as Early as 2040:

This was based on confusion of the use of “price” in that section with its use of “tax” and the authors of this paper most likely made the same mistake. The distinction is set out clearly in the first sentence of this section but it is easy to miss such things I suppose:

The price of carbon assessed here is fundamentally different from the concepts of optimal carbon price in a cost–benefit analysis, or the social cost of carbon

The IPCC give these eye wateringly high prices:

For instance, undiscounted values under a Higher-2°C pathway range from 15–220 USD2010 tCO2-eq−1 in 2030, 45–1050 USD2010 tCO2-eq−1in 2050, 120–1100 USD2010 tCO2-eq−1 in 2070 and 175–2340 USD2010 tCO2-eq−1 in 2100. On the contrary, estimates for a Below-1.5°C pathway range from 135–6050 USD2010 tCO2-eq−1 in 2030, 245–14300 USD2010 tCO2-eq−1 in 2050, 420–19300 USD2010 tCO2-eq−1 in 2070 and 690–30100 USD2010 tCO2-eq−1 in 2100.

But these are not suggestions for prices for carbon taxes. When it goes on to discuss taxes it says:

Furthermore, a mix of stringent energy efficiency policies (e.g., minimum performance standards, building codes) combined with a carbon tax (rising from 10 USD2010 tCO2−1 in 2020 to 27 USD2010 tCO2−1 in 2040) is more cost-effective than a carbon tax alone (from 20 to 53 USD2010 tCO2−1) to generate a 1.5°C pathway for the U.S. electric sector (Brown and Li, 2018).

I.e. it's recommending a range of carbon tax rising from $20 in 2020 to $53 in 2040 if you use a carbon tax alone for the US electricity sector, but a mix of carbon taxes of $10 rising to $27 with stringent energy efficiency policies is more effective.

$10 rising to $27 is hardly "much higher" than $15.25.

But it goes on to say that an even lower carbon price of $7 per ton is optimal:

Likewise, a policy mix encompassing a moderate carbon price (7 USD2010 tCO2−1 in 2015) combined with a ban on new coal-based power plants and dedicated policies addressing renewable electricity generation capacity and electric vehicles reduces efficiency losses compared with an optimal carbon pricing in 2030 (Bertram et al., 2015b).

I.e. a ban on new coal based power plants and dedicated policies addressing renewables and electric vehicles works better even than the best carbon tax pricing.

It goes on

A bottom-up approach shows that stringent minimum performance standards (MEPS) for appliances (e.g., refrigerators) can effectively complement explicit carbon pricing, as tightened MEPS can achieve ambitious efficiency improvements that cannot be assured by carbon prices of 100 USD2010 tCO2−1 or higher (Sonnenschein et al., 2018).

I.e. even a carbon tax of $100 per ton is not as good as setting stringent minimum performance standards.

This shows that anyone who signed the letter either doesn't care about inaccuracies in a letter they sign, or they didn't check the cite.

Also whoever peer reviewed it didn't check that cite.

Climate change is predicted to greatly affect marine, freshwater, and terrestrial life, from plankton and corals to fishes and forests (IPCC 2018, 2019). These issues highlight the urgent need for action.

Vague again, what does "greatly affect" mean?

The climate crisis has arrived and is accelerating faster than most scientists expected (figure 2, IPCC 2018).

What does "faster than most scientists expected" mean? The IPCC is not cited by section number, no idea what they are referring to there. Figure 2 is an array of charts, not from the IPCC, with no comparisons with what previous reports predicted and indeed the charts are not discussed or expanded on.

It is more severe than anticipated, threatening natural ecosystems and the fate of humanity (IPCC 2019)

The IPCC 2019 report does NOT say it threatens the fate of humanity, and this, by far their most dramatic claim (risk of human extinction) again has no section number cite.

So the only cite of the IPCC reports by section number is the one on taxes which is incorrect. The others are vague statements that are not made precise and one that is manifestly wrong, that the IPCC said that it threatened the fate of humanity - many news stories suggest that but the IPCC do not say this.

Indeed it’s hard to see how anyone could even think this. How can a world where only a small fraction of the Greenland ice has melted (even at “business as usual”) be too hot for humans to survive and lead to human extinction?

The rightmost drawing here with all the ice melted is not 2100, it's the year 3000.

Image credit: UAF Geophysical Institute

from: Contribution of the Greenland Ice Sheet to sea level over the next millennium (study published: June 2019)

It is not certain even then. Between 72 and 100% lost according to a recent study.

That’s “Business as usual”, i.e. continuing to burn fossil fuels as we are now, with no reductions in CO2 emissions at all through to the 23rd century, eventually stopping mainly because we run out of fuels to burn.

What thought process can lead someone to conclude that such a world is uninhabitable by humans?

It’s always vague statements like this and not cited to any detailed reasoning of how they think humans could go extinct.

Even a 10°C rise, which we can’t reach until maybe 2200 under “Business as usual” is not an uninhabitable world (though not one we want to transition to quickly of course). It's coconuts in the Mediterranean, not coconuts in Greenland!

They don't use a section number cite for that but do for the carbon tax. Why not cite by section number for this claim that it threatens the fate of humanity?


It bases its ideas of a tipping point on only one cite, a paper called the “Trajectories of the Earth System in the Anthropocene”, which is just discussing possibilities that if they happened would only fully unfold over thousands of years (when all the ice in Greenland and Antarctica that can melt, melts) - there is no timescale.

The paper has no cites for their second claim that parts of the world will become uninhabitable, unless it is this cite (which cites the previous sentence in the paper).

In detail:

Especially worrisome are potential irreversible climate tipping points and nature's reinforcing feedbacks (atmospheric, marine, and terrestrial) that could lead to a catastrophic “hothouse Earth,” well beyond the control of humans (Steffen et al. 2018). These climate chain reactions could cause significant disruptions to ecosystems, society, and economies, potentially making large areas of Earth uninhabitable. [uncited]

Their “potentially making large areas of Earth uninhabitable” doesn’t have any timescale. It is not cited to any papers so there isn’t anything there to drill into to find out more. “Catastrophic” is another of those vague words that is not explained by the cite.

They don't explain that Greenland can only melt over thousands of years.

It doesn't explain what "uninhabitable" means. Humans can withstand high levels of heat in deserts, by sweating to lose heat, but what we can't withstand is heat combined with high humidity.

Does it mean

  • you can't work in the paddy fields for a few days during the worst heatwaves? Starts to happen for hottest parts of China (for instance) at around 4 C (paper here)
  • need air conditioning to survive on the hottest day in the hottest heat wave every decade or so? (Starts to happen in the Persian gulf at around 7 C according to one paper, see the MIT press release - not likely to get there this century
  • that there's a 1 in 10,000 chance of dying if you don't take the proper precautions such as drinking enough water, seeking shade at hottest times of day etc (definition of "deadly heat" in this paper) - see Global risk of deadly heat’ is about heatwaves that already affect 30% a year - elderly and vulnerable should take precautions
  • Or is the Sahara desert uninhabitable because you need a supply of water to live there? Surely it can’t be that because large parts of Earth are already desert or ice sheet -

The heat waves such as we had in Europe this last summer are of course happening already. That is uncontroversial

There is high confidence that heat waves will increase in frequency, intensity and duration into the 21st century and under high emission scenarios heat waves by the end of the century may become extremely long (more than 60 consecutive days) and frequent (once every two years) in Europe, North America, South America, Africa, Indonesia, the Middle East, south and south east Asia and Australia Changes in extreme temperatures, heat waves and drought

But that's not what most people would understand it to mean, Europe wasn't "uninhabitable" this summer. Nobody needs to die in those conditions if they take the right precautions. Most just enjoyed the fine weather. For details see ‘Global risk of deadly heat’ is about heatwaves that already affect 30% a year - elderly and vulnerable should take precautions

Also, they don’t say on what timescale parts of the Earth could become "uninhabitable" A thousand years in the future? This century? Again, that sentence is not cited,. so you can't go to a cite to find out what they meant. There is no way for those who signed this paper to know what it meant by "uninhabitable" or on what timescale.

If it is based on that “Trajectories of the Earth System in the Anthropocene”, which is their only cite, it's talking about something that might possibly (not certainly) unfold over maybe tens or hundreds of thousands of years for everything to equilibrate, with no attempt to quantify the timescale. It doesn't override the IPCC reviews. They are looking in a different direction, at the long term equilibrium which unfolds over thousands of years which is not a priority of the IPCC reports. And this also has no clear definition of the term "inhospitable" and doesn't use the word "uninhabitable" at all.

This matters if our policy decisions are supposed to be based on this - we need to be precise as the IPCC are.

This is how the author “Trajectories of the Earth System in the Anthropocene” describes his work to New Scientist:

The team stress that they are pointing out a potential danger that needs study, not that they have shown conclusively that this will happen. “We are discussing a possibility, not a probability, and ask the scientific community to put our scenario to the test,” says Schellnhuber. Indeed, other climate scientists that New Scientist spoke to – who did not wish to be named – expressed scepticism at its findings although others thought it was reasonable.

Global warming may become unstoppable even if we stick to Paris target

That paper is not something you should use as your single cite to try to overturn the IPCC and IPBES reports.

My comments on that paper are here:


This paper doesn’t cite the IPCC on tipping points, but let’s look and see what it says. There is nothing in the IPCC to support this sentence:

Especially worrisome are potential irreversible climate tipping points and nature's reinforcing feedbacks (atmospheric, marine, and terrestrial) that could lead to a catastrophic “hothouse Earth,” well beyond the control of humans

Any such finding would have been headline news and the main point in their media press conferences and presentations. There is no way that this is just tucked away as some forgotten section detail somewhere. So I can say confidently that this is not in any of the reports from the IPCC - we would know, would have a statement quoted over and over and section citing if they did say this.

Their big finding was that every half degree matters. They did find that there is a significant difference between 2 C and well below 2 C.

They did find tipping points for the Greenland and West Antarctic ice, but these unfold over thousands of years, plenty of time to step back from that particular cliff using carbon capture and storage over many centuries.

Greenland ice has a tipping point between 0.8°C and 3.2°C, median 1.6°C. If we cross that tipping point (it is possible we already have) the result is very dependent on future climate, between 80% loss after 10,000 years and complete loss after 2,000 years. The threshold for Western Antarctica (and sectors of Eastern Antarctica) is hard to estimate but probably between 1.5 to 2°C. Most of Eastern Antarctica continues to accumulate ice, as it did through the previous interglacials. See Sea level

Tipping points are uncontroversial over thousands of years. It is possible we have passed the tipping point for Greenland to melt entirely over hundreds of thousands of years - but if we have, we won't yet notice anything much by 3000 unless we continue at "business as usual".

Even with “Business as usual” continuing current emissions through to 2200 then it takes until 3000 for Greenland to melt completely.

How long does it take for the Greenland ice to melt completely?

The melting of the Arctic sea ice is not a tipping point either, according to the report (see Sea Ice). As soon as we reach zero emissions the Arctic ice then is in steady state and will slowly being to heal as some of the excess CO₂ leaves the atmosphere.

They discuss large scale singular events in the 2018 report but none of these are tipping points in this sense: RFC 5 – Large-scale singular events

Large-scale singular events are components of the global Earth system that are thought to hold the risk of reaching critical tipping points under climate change, and that can result in or be associated with major shifts in the climate system.

There they list

  • the cryosphere: West Antarctic ice sheet, Greenland ice sheet
  • the thermohaline circulation: slowdown of the Atlantic Meridional Overturning Circulation (AMOC) (Best estimates and ranges for the reduction based on CMIP5 simulations are 11% (1–24%) in RCP2.6 and 34% (12–54%) in RCP8.5 (AR5)
  • the El Niño–Southern Oscillation (ENSO) - the number of El Nino’s expected to double (one event every ten years) under 1.5°C of global warming and the pattern to persist for a century after stabilization
  • The critical role of the Southern Ocean as a net sink of carbon might decline under global warming, and assessing this effect under 1.5°C compared to 2°C of global warming is a priority.

The most famous tipping point is probably the clathrate gun hypothesis - this is now effectively disproved

See also my:

Those dramatic claims (together with the timing immediately after Trump’s announcement that the US is going to withdraw from the Paris agreement) are the reason it hit he mainstream media and became viral and it is all based on that one paper (or nothing).

Why not cite the IPCC reports by conclusions and section numbers? Or if they disagree, at least cite the reports then explain that they disagree with their conclusions and on what basis.


Their whole population paragraph is cited to a single paper that is self acknowledged to be controversial.

Still increasing by roughly 80 million people per year, or more than 200,000 per day (figure 1a–b), the world population must be stabilized—and, ideally, gradually reduced—within a framework that ensures social integrity. There are proven and effective policies that strengthen human rights while lowering fertility rates and lessening the impacts of population growth on GHG emissions and biodiversity loss. These policies make family-planning services available to all people, remove barriers to their access and achieve full gender equity, including primary and secondary education as a global norm for all, especially girls and young women (Bongaarts and O’Neill 2018)

Dr Thomas Newsome, of Sidney University, one of the authors interviewed by ABC Australia says this as their top message (4:42 into this video interview with ABC News in Australia).

In some countries where the population growth is really high there may be room there for other countries to support some of that population growth, but ideally in terms of limiting population growth, we need to provide education and birth control tools for developing countries to further reduce their fertility rates and birth rates.

I.e. his idea is that the solution to population growth is to give everyone in poor countries contraceptives and access to family planning!

Their cite does NOT say

“The world population must be stabilized—and, ideally, gradually reduced”.

It is a paper with a question in the title:

Global warming policy: Is population left out in the cold?

It opens with the question:

Would slowing human population growth lessen future impacts of anthropogenic climate change?

It then goes to argue its case saying that it seems an obvious “yes” because of the 4 billion extra people expected on the planet and because many of the least-developed countries have family planning programs and see population growth as “an important component of vulnerability to climate impacts”.

The focus of this cite is on population growth in the least-developed countries, all the way through. Not for the world as a whole.

It says that

But despite this evidence, much of the climate community, notably the Intergovernmental Panel on Climate Change (IPCC), … is largely silent about the potential for population policy to reduce risks from global warming.

So to start with it is not saying it is imperative it is asking if slowing human population growth would reduce the impacts of climate change and particularly for least developed countries and saying that the IPCC should cover this more.

As you read to the end of the paper, its argument is that the way to solve the population problem in poorer countries is to give them access to better education and contraception.

Governments around the world now support the conclusions of the ICPD, confirmed by the SDGs, which call for a human rights–based approach and for women everywhere to have the right to freely choose when and how often to get pregnant (14).

In the article they mention particularly a successful family planning campaign in Bangladesh. And yes this is a top commitment of Bangladesh. But not just contraception. A very important component is also deploying midwives and and clinical teams to help with childbirth, ending child marriage, and helping adolescents. Family Planning 2020

Though it’s true that the least developed countries do often focus on helping with family planning and to help their people to have less children if the wish to, if you look at other population articles the discussion is more nuanced than this paper suggests.


First, our population is already stabilizing naturally. It is set to level off at 11 billion by 2100 with the middle of the range projections, and 9 billion by 2050 with more optimistic projections.

This is not because of scarcity and lack of resources. It is because birth rates fall as nations become more prosperous Indeed we have already almost reached peak child.

When will the world reach 'peak child'?

Our population is growing still mainly because we are living longer, between ten and twenty years longer than 50 years ago (sometimes more than twenty years longer in the poorer countries).

For more details see also charts from: World Population Growth

The population is expected to peak in Asia long before 2100, around 2050:

Chart from: World Population Growth

The projections for 2100 are very dependent on projections for Africa. If there is greatly increased food security, education for women, higher education, women in work, reduced child mortality, then the African population may also peak by 2050 like the Asian one.

The problem in Africa is that families feel they need to have many children to make sure at least one or two of their children reach adulthood and are also well enough and strong enough to look after their farm or smallholding when they get old.

There are signs already of the younger population having lower birth rates. If you factor in changes due to higher levels of education, the result can be anywhere between 6.9 and 12.6 billion by 2100 according to another study. See The human core of the shared socioeconomic pathways: Population scenarios by age, sex and level of education for all countries to 2100

  • By 2100 world population ranges from 6.9 (SSP1) to 12.6 billion (SSP3).

Here are three of their six scenarios, notice what an effect higher education has on the population growth:

It’s interesting to notice how much of an impact tertiary education (dark blue) has. Education of women is especially important because almost universally, the more educated women have lower levels of fertility.

They found that more education for women can knock a billion people off the projection for 2050, that's really near future!


Although sub saharan Africa is the region with the greatest projected population growth, it is also one of the least developed regions, with a low population density, 51 people per square kilometer compared to 460 per square kilometer for India, and 153 per square kilometer for China (which has large areas of desert).

It is also one of the regions with the greatest potential for increasing crop yields to feed everyone. That is because the green revolution which made such a difference to crop yields in Asia, Europe and the Americas in the 50s through to the 70s largely bypassed Africa.

It continues to use unimproved crops and low yield methods of irrigation and agriculture. It can’t just import methods from the rest of the world, but needs local solutions adapted to their specific needs and crops, including work on crop improvement for Africa.

This chart shows how big the gap is between the African countries and the top yielding countries in cereal yields per hectare.

Yields and Land Use in Agriculture

There is a remarkable ten-fold difference between the yields in sub-Saharan Africa and the yields in the US and China.

There’s a huge potential for improvements in African agriculture. That’s the motivation behind the Alliance for a Green Revolution in Africa (AGRA). See also AGRA

So, the complete picture, if you read the literature on population growth, is a lot more nuanced than the idea behind their cite that we need to make sure all the poor people have access to contraceptives and family planning advice to magically solve population growth!

They need reduced infant mortality, better health care, better education, and at the same time an agricultural revolution. Also, as one of the less populated regions of our world with a huge agricultural potential, just from efficiency improvements using the same land, it’s not such a huge concern as it seems in the global picture.


If your children, as they grow up, live in a carbon zero country, their emissions are zero. If you are still alive, in the society they helped create, your emissions become zero also.

Your later zero emissions may indeed depend on the work of the young children who you brought into your society.

Our children are part of the transformative change of society. Many of them are in the forefront of changing society.

We need our young.

We have more than enough food for everyone on all scenarios and especially if we transition to more sustainable lifestyles, less food waste, and eating less meat and the right kind of meat.

My post here goes into the population growth question in detail with many cites:

A paper published in 2017 claimed that the most effective climate action you can do at a personal level is to have one less child.

This was criticized for multiple accounting - it attributed CO2 emissions for children and even grandchildren to their parents, and it also assumed that we will never achieve carbon zero.

For instance Finland aims for zero emissions by 2035, and after that, to be carbon negative. The UK and California aim for zero emissions by 2050. These pledges may increase. By 2035 people in Finland including their children, will be contributing zero emissions.

So no, we don’t have to urgently stop and reverse population growth, though it is beneficial to reduce child mortality, increase access to medical care and midwives, increase prosperity, improve education standards and health care. As part of that process then it is appropriate of course to have effective family planning advice and work with related issues in society such as child marriage as Bangladesh has done.


The two figures in the paper are downright baffling.

Despite 40 years of global climate negotiations, with few exceptions, we have generally conducted business as usual and have largely failed to address this predicament (Figure 1)

Click through and you see a page of graphs like this, how is this evidence that we are not acting? What is it even supposed to mean? This is a selection of four out of fifteen graphs:

The gray dots for the tree cover loss are all over the place, and it doesn’t mention afforestation. Europe and north America and much of Asia have had forest cover increasing ever since 1990

The gray dots for the tree cover loss are all over the place, and it doesn’t mention afforestation.

The gray dots for the tree cover loss are all over the place, and it doesn’t mention afforestation.

Europe and north America and much of Asia have had forest cover increasing ever since 1990 SOFO 2018 - The State of the World's Forests 2018

Also deforestation of temperate forests has almost stopped and if you take a longer term perspective, deforestation of tropical rainforests has reduced from a peak in the 50s to 70s

Forests- Our World In Data

Here are some that have forests increasing: France, Spain, China, Ghana, Vietnam, Italy,

Forests- Our World In Data

That’s through to 2015, and a lot is happening since then.

In 2017 around 1.5 million volunteers planted more than 66 million trees in the state of Madhya Pradesh in India.

Topping that, Ethiopia planted 353 million trees in 12 hours in July 2019.

Ethiopians Plant 353 Million Trees In 12 Hours - World Record - Aim To Plant 4 Billion Total This Summer - What If UK Did Same?

And what is the GDP figure doing there. What does it have to do with the price of cheese? (that’s a saying we have in the UK when you see an irrelevant bit of data and don’t know why it is there)

The GDP of California is increasing while the CO2 emissions are decreasing - are they saying that GDP is a measure of CO2 emissions??

California Greenhouse Gas Emissions for 2000 to 2017

It’s the same for biodiversity. Recycling generates GDP from waste products. If you reverse desertification, it’s restorative and again generates GDP. If you do conservation work to save a species, it’s also part of GDP growth that’s positive. As an example, already in the UK:

In the UK, uses of biodiversity directly supports more than 35,000 full-time equivalent (FTE) jobs and contributes more than £4.8 billion to GDP. In addition, environment-related activities are estimated to support around 500,000 jobs and £18.6 billion of GDP.

Economies, Employment, Environment - The RSPB

The UK has also seen GDP growth as a result of its energy policy which has reduced emissions while increasing GDP. Both of those target zero emissions by 2050.

Sustainable continuing economic growth on a finite planet - how is that possible?

The supplementary data says nothing except to give the sources for the data and adds

Although the data used are from sources believed to be reliable, no formal accuracy assessment for these datasets has been made by us and users should proceed with caution.

They continue with

“The climate crisis has arrived and is accelerating faster than most scientists expected (figure 2, IPCC 2018). It is more severe than anticipated, threatening natural ecosystems and the fate of humanity (IPCC 2019)."

The IPCC cites don’t support what they say as we see, so the full weight rests on this figure, another fairly random seeming set of graphs, here are six of them:

?? Again no explanation anywhere of how these graphs relate to their thesis in that sentence that

It is more severe than anticipated, threatening natural ecosystems and the fate of humanity

As interviewed by ABC news he says (2:10 into the interview with ABC news) he wants his indicators to be repotted to the government every month and these reports shown on the TV news.

Ideally these indices and indicators would be reported back to the government at monthly levels. It would be great to see it on 7 o-clock news reported back to the community how we are tracking in terms of forest loss, greenhouse gas emissions and things like that. And if they are putting in the right policies, if they are putting in the right steps we should see the trajectories of those graphs changing in a positive way

??? World GDP on the news every month - because GDP is somehow bad?


The paper is here

World Scientists’ Warning of a Climate Emergency

This is about the ones in 2017 and 1992.

World Scientists' Warning to Humanity - Wikipedia


The signatures are in a downloaded zip. Most are other disciplines, forestry, geology, mathematics, many don’t say. Out of those 11,000 there are 190 that have the word "climat.." e.g. climate or climatology in their description.

I can't see the climate science co-chairs for the IPCC: Debra Roberts, Jim Skea, Eduardo Calvo Buendía, or any of the others from the IPCC Bureau Portal - IPCC

Not that I'd expect it - how could they sign something that contradicts what the IPCC says? Or something that says such vague and imprecise things?

As for those who did sign it, those media reports can seem convincing if you research in a different topic area and are used to them reporting reliably on your own area of expertise. Also when panicking you don't think so clearly

As one person I help said, an academic in a different area of the sciences:

I like to think of myself as a smart person, I am a tenured professor, a scientist, so I should be able to judge the credibility of these stories. However, oftentimes scientists would not speak up against these stories or even tweet about them in a way that implied endorsement. This is not my area of expertise and if scientists in this field agree they these stories are accurate, if high quality newspapers write these things, then I start believing that they must be true.

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Their recommendations are for the most part fine, similar to IPBES and IPCC except the population recommendation


On the countries, of the top 7 emitters, one is exiting the deal but still has reducing emissions (US), two are under achieving (Canada and Australia) one is doing rather little, but keeping well within its pledge which is very weak (Russia) and three are increasing their commitments (China, the EU and India)

They have to increase ambitions to get to 1.5 C but we are already at 2.9 C. We've reduced this by over a degree with the pledges since 2015, and we have another 1.4 C degrees to go to get down to 1.5 C. This is the harder part but we have new pledges in 2020, 2025, 2030 and so on to do this!

How well are countries doing with their 2015 Paris pledges?

The IPBES report is far better than this. They don't have any new research here that the IPCC and IPBES haven't covered already.

See also my


If you are depressed about climate change this may help:

About dealing with sea level rise


The tipping points they mention mainly play out over scales of centuries to millennia.

Those tipping points with carbon negative technology which we may be able to do in a large scale way in the future. Although we don't have this mature yet, we may well later this century or in subsequent centuries. The lowest cost / lowest tech proposal might be seaweed farms of giant kelp floating in the deep oceans:

There is also considerable uncertainty on some of the projections, such as the effect of permafrost thaw over century timescales. For instance this shows the range of projections for change in ecosystem carbon through to 2300 according to one 2018 study cited by the 2019 Ocean and the Cryosphere report:

Figure 3 from Dependence of the evolution of carbon dynamics in the northern permafrost region on the trajectory of climate change

At present we don't know if the Arctic permafrost will be a carbon source or a carbon sink as the grass, roots, animals etc locked in the permafrost thaw out and decompose and as tundra, peat bogs, trees, grassland and shrubs grow in the places which used to be ice. As you see from that figure (and also born out in other research papers), the permafrost can be anything from a significant loss of more than 600 GT to a gain of over 100 GT by 2300 on RCP 8.5 by 2300. It’s hard to know for sure what will happen as the permafrost thaws over thousands of years, and what this will contribute to the very long term carbon dioxide budget.

Remember with a tipping point that unfolds over thousands of years, then you also have thousands of years to do something about it with whatever technology we develop after another thousand years of our civilization.

It may be too late already to stop the Greenland ice melting tens of thousands of years into the future, except by removing CO2. The plus side is though that at the same time we have probably prevented the next ice age 1500 years from now and that may be more important to them than Greenland's ice melting.

It's so hard to foresee what future generations may need, I think our top priority should be to eave the world in a good state for the next generation and they can adjust the CO2 as needs be over following centuries.

If Greenland’s ice melting is important they can find a way to sequester 100 ppm (say) over the next 1000 years. If not they may even feel they want to increase the CO2 levels to prevent far future ice ages. We can't know in advance - it would be hard enough for someone in 1950, say, to make such decisions about us, 70 years later never mind 1000 or 10000 years later.


If you see any mistakes in this however small, or have any suggestions or questions, be sure to comment below, thanks!

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