Biden Crowing about Small Gas Declines Now

Joe Biden appears to have fallen into political delusion.

Joe Biden is continuing his your-family-is-doing-great tour.

After months of telling America that nothing can be done about gasoline prices, Biden is on Twitter this morning bragging about gasoline declines that he says are biggest in ten years.

The supine incompetence of the Biden administration continuing today may embarrass this corporatist Democrat, but this presidency and Party appear beyond embarrassment.

We've now hit more than six straight weeks of declines, making this the fastest drop in gas prices in over a decade.

— President Biden (@POTUS) July 28, 2022

Few families are cheering the news knowing gasoline prices remain a severe drain on families, though Biden appears not to be aware of this fact.

Climate Change - The Better Graph on the Wall

Global Surface Temperature since 1880, and temperature
anomalies - Figure One above , A Better Graph

Slow-motion catastrophe in a graph

Empirical scientists are not bottom-line people. They compile data, access, and then offer conclusions supported, conclusions provisional in nature and ever-changing as more data come to light.

Drs. James Hansen and Makiko Sato are investigating the composition and dynamics of Earth's atmosphere using data pointing to climate change. This work comes as Republicans in America take refuge in denial, and a collective burying of heads in the sand.

It happens the phenomenon Hansen, Sato and colleagues are looking at bears on the fate of life on Earth. They probe the causes and dynamics of global warming, climatic forcings, and in a separate realm quantify global temperatures.

Hansen and Sato offer humanity a new graph accessible to the most foolish, coming six weeks after Hansen called for nuclear power with its attendant hazards and anomalous release of radiation, to replace the energy-production disaster Homo Sapiens imposed on the planet. (This critical nuclear power piece was widely ignored but suggests how dire conditions are in Earth's atmosphere.)

I wrote Dr. Hansen asking for a definitive public conclusion that catastrophic climate change is irreversible, and we as a planet are beyond the point of no return from major life-altering qualities of Earth.

Scientists have little use for making such statements, it's outside the scope of their enterprise, and Hansen and Sato are as likely as not buried in writing their next paper.

Below is a graph including a best estimate showing the projected change in global surface temperatures that is alarming and devoid of adjectives.

That we are beyond the point of no return appears a conclusion supported by the evidence, and mitigation through coordinated geo-engineering is the needed project universal-in-scale, hence a mere conceit.

Hansen and Sato publish this graph showing annual global surface temperatures relative to 1880-1920, illustrating the anomaly, (change and deviation from 'normal', expected values), in global surface temperature the last several decades.

We live in anomalous times.

As carbon and methane emissions are the primary cause for the increase in temperature change and no change in emissions are expected, we can predict values represented in the graph will move upwards and not down.

Here's the new graph, followed by Hansen and Sato's explanation why this graph is instructive to the matters at hand, (a simple 'we're fucked' would have been revealing too as the rate of temperature change looks to be increasing with higher annual temperatures):

Global Surface Temperature since 1880, and temperature anomalies
Figure One, A Better Graph

Fig. 1. Global surface temperature relative to 1880-1920 based on GISTEMP analysis (mostly NOAA data sources, as described by Hansen, J., R. Ruedy, M. Sato, and K. Lo, 2010: Global surface temperature change. Rev. Geophys., 48, RG4004. We suggest in an upcoming paper that the temperature in 1940-45 is exaggerated because of data inhomogeneity in WW II. Linear-fit to temperature since 1970 yields present temperature of 1.06°C, which is perhaps our best estimate of warming since the preindustrial period.

A Better Graph

by Web Team | September 26, 2016
Category: Blog

A Better Graph

26 September 2016

James Hansen and Makiko Sato

Sorry to have temporarily stopped writing Communications – was working on a paper that we hope to soon make available. But here is something useful: a better graph.

For decades we have reported/updated the global temperature record, showing the calendar-year annual-mean temperature, usually with the 5-year running-mean included. I submit that the graph below is not only more beautiful, but more informative and it can be usefully updated every month rather than once a year.  The 12-month running-mean takes out the seasonal cycle just as well as the calendar-year mean and includes the calendar-year mean (black squares).  The 11-year running mean does a pretty good job of taking out solar cycle variability and shorter-term variability such as the Southern Oscillation.

Note that the calendar-year means tend to fall a bit below a preceding maximum in the 12-month running mean, so the 2016 mean will probably fall a bit below the current +1.3°C warming relative to 1880-1920. That small drop is usually related to the phasing of the El Nino cycle relative to the calendar year.

BTW, this graph also switches to 1880-1920 as a base period, because of the widespread interest in the magnitude of warming relative to pre-industrial time. Alternatively, one might argue for an earlier base period, say 1700-1800, but the data are much poorer then and the difference in global mean is only about +0.1°C ± 0.1°C (1880-1920 slightly warmer than 1700-1800), so it is of no practical importance.
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On Reluctance to Use the Word, Dangerous, to Warn of Threats to the Planet in Climate Science

Anthropogenic, [human], carbon release rate unprecedented during the past 66 million years is the title of a paper published this month in Nature.

In 2007, Dr. James Hansen wrote a work using the word "dangerous" in the sub-title, a reference to the predictable catastrophic consequences of large sea level risings caused by human energy-system gasses.

Hansen emphasized the subsequent reticence many in the scientific community maintain towards the alarming connotations of the word, dangerous.

Hansen is the former Director of the NASA Goddard Institute for Space Studies, and is Adjunct Professor at Columbia University’s Earth Institute, where he directs a program in Climate Science, Awareness and Solutions.

In 1998, Hansen testified before Congress at the Senate Energy and Natural Resources Committee revealing "global warming caused by pollutants in the atmosphere, known as the 'greenhouse effect,''' (Shabecoff, New York Times).

The spectacle of massive policy consequences following Hansen's historic testimony on the June 1988 global atmospheric trajectory of greenhouse gasses revealed by Hansen never occurred.

Political indecision is perhaps not shocking.

"Carl Sagan tells the story of how, after he had conducted a briefing for members of Congress about nuclear winter [in the mid-1980s], a participant called him aside and said, ‘Carl, if you think the mere prospect of the demise of humanity is going to change the way people in Moscow or Washington think, you clearly haven't spent much time in either place,'" (Alan Robock, (Rutgers, 1989)).

Hansen warns of a concomitant danger to politically passive accomplices: The widespread and severe affliction of scientific reticence, which will, Hansen warns, "severely diminish our chances of averting dangerous climate change."

Writes Dr. Hansen yesterday:

Dangerous Scientific Reticence
23 March 2016

James Hansen

Several years ago I wrote a paper [1] on scientific reticence, naively thinking that drawing attention to the phenomenon might ameliorate its incidence. Specific reference then was to likelihood of large sea level rise, which also is a central topic in our current paper [2]. However, here I address a broader issue of scientific reticence, because, I believe, the affliction is widespread and severe. Unless recognized, it may severely diminish our chances of averting dangerous climate change.

It may be clearest if I describe two of my experiences in the last few years, and then comment on why this topic is important. However, I want to emphasize that my experience with Atmospheric Chemistry and Physics was exceedingly good.  First, I recommend their open procedure, i.e., publication of a discussion version of the paper in ACPD, and a final version in ACP, if the paper passes review, and publication of Comments by the scientific community, referee reports, and author responses, which is helpful for public understanding of the publication process.  Second, we appreciate the exceptional help of all people at ACPD and ACP, and are especially grateful to the ACP editor for his generous work in support of publication of our paper and the paper’s title. Without his help the paper may still be unpublished.

The paper’s subtitle differs between the ACPD and ACP versions of the paper.  The main issue about the title concerned the word “dangerous,” as in the case of an earlier paper[3] that provided the scientific basis for a law suit aimed at requiring stronger action by the U.S. government to avert dangerous climate change. We ultimately lost that case at the United States District Court Level, one level below the Supreme Court. Recently 21 youths and I have filed a new case in which we have made clearer the Constitutional rights of young people and future generations, as described in my recent Communication Our Children’s Right to a Viable Future.

I submitted the earlier paper³ initially to PNAS, [Proceedings of the National Academy of Sciences], along with reviews by two relevant scientists, one an NAS, [National Academy of Sciences], member, both of whom gave the paper the highest rating. As an NAS member, I expected that to be sufficient for publication, but the Editor gave the paper to an anonymous Editorial Board member who insisted that we remove “normative” statements from the paper. After multiple iterations this anonymous Board member informed me that “dangerous” was normative. We thus withdrew the paper from PNAS, and published it in PlosOne. The paper provided a prescription for how fast fossil fuel emissions must be decreased if CO₂is to be returned to 350 ppm by 2100, information needed to define a remedy to keep global temperature close to its Holocene range.  The dispute over normative statements delayed publication a year, but did not prevent eventual publication.  The fact that we had to use a draft of an unpublished paper in this initial court case, may or may not have affected the outcome of the case.

Our new paper² strengthens the case that global warming of even 2°C would have deleterious effects and heightens the urgency of phasing out fossil fuel emissions.  However, the word “dangerous” again raised flags among referees (labeled R1, R2, R3 and R4) and the editorial board. Their full reviews are published on the ACP web site.  Here (the following section in smaller font) is my initial response to the editor about the objections to the paper title:

Paper Title

You mention that referees R3 and R4 question the title of the paper. The issues raised about the title concern the word “Dangerous” in the title, and they are important because they get at the very heart of our paper and the overall topic of human-made climate change.  I think that the discussions raised are pertinent and I am glad that you give us the chance to propose a title and show that it is well motivated.

I believe that you may have misread the relevant comment of R4. R4 notes that a major goal of our paper is to define “dangerous anthropogenic interference”, [anthropogenic means relating to, or resulting from the influence of human beings on nature], and he then quotes the 1992 United Nations Framework Convention on Climate Change (UNFCCC), as follows: “…to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.”

R4 then says that our paper: “…significantly advances this quest for a more quantified definition of such human impact. Very few serious efforts have been made to arrive at a useful definition of ‘dangerous anthropogenic interference’.  Previous efforts focused on sea level rise have been less rigorous, I believe, with less analysis of the coupling of ice meltwater with oceanic dynamics.”
R4 does not mention the paper’s title or criticize it, but explicitly recommends publication of the paper.

R3, on the other hand, does criticize the title and does so by referring to the UNFCCC, but his reference is not correct. The word “dangerous” appears once and only once in the UNFCCC, namely in the most fundamental phrase of the Convention, which is given in the inset phrase above.  R3 says that “…in the climate change debate, the term ‘dangerous’ has been given a rather precise definition in Art 2 of the UNFCCC, namely a change that doesn’t allow ecosystems to adapt, that threatens the food production and that prevents economic development in a sustainable manner”.  This is a rephrasing of Article 2 that seems to slightly change its meaning.  Let us look at Article 2 in its entirety:

The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.

Article 2 thus uses the word “dangerous” with regard to the level of greenhouse gases in the atmosphere. The ecosystems/food/economics sentence refers to timeframe in which that level should be obtained.

The word “dangerous” is not further defined, and that is probably for good reason: the public understands what “dangerous” means. The concept was understood before humans had a language to express it.

Let us give an analogy. Say there is a poorly lit street frequented by gangs, thugs and robbers, which police reports indicate has continually been the location of crimes, and newspapers have reported such. A person looking down this street late at night and seeing a number of loiterers, one seemingly with a blackjack in his hand, might well conclude that it would be dangerous to go down that street.

What is shown in our paper is analogous. It would be dangerous in a sense that people would understand.

One suggestion is that we enclose the word dangerous in parentheses. That would not be right, because it implies that we mean something different by the word dangerous than what the public understands.

However, we mean exactly what the public understands. Or the parentheses could mean that the UNFCCC meant something different by the word than what the public understands, but they mention the word only once, clearly expecting that the word will be understood.

A second suggestion is that we write that we have shown that 2°C warming is “potentially dangerous”. That also is wrong. Consider this: When a person decides not to walk down that street, is it because he has concluded that it is absolutely certain that he will be mugged if walks down the street?  No, dangerous does not imply certainty of harm.  Dangerous means that there is a serious threat that he will be harmed. [I note that R2 suggested “potentially dangerous”; probably you meant to refer to R2, rather than R4.]

There is a very important issue at play here: the relevant scientific community, in our opinion, has been exercising self-censorship in its warning to the public about the danger of human-made climate change. It would be difficult to overstate the threat of increasing human-made climate change, which we suggest threatens to bring about some of the greatest injustices in the history of the planet: of current adult generations to young people and future generations, and of people of the industrialized North to people of the South, as climate change is due mainly to emissions from nations at middle and high latitudes.

As R4 discusses, our paper makes an important contribution toward defining dangerous anthropogenic interference with the climate system. We do not want to self-censor this clear, substantiated conclusion.

As a compromise, we suggest that “highly dangerous” be changed to “dangerous” in the title, which has several merits. (1) it slightly shortens the title, (2) it avoids the need to define the difference between “dangerous” and “highly dangerous”, (3) it makes the title less “journalistic”, which was a concern of R3.  I hope that the Editor agrees that our proposed alternative phrasing for the title is well motivated.

I hoped my response above was a winning argument, but the editor (who interacted with higher levels, including the editorial board, and was being as helpful as possible to our case), warned that I should not include the “dark street” discussion in my official response to the journal, that such analogy is relevant to the public, but our paper was written for scientists not for the public.

In fact, we were in part writing for the public. I had assembled a stellar international group of co-authors, for this paper as well as for our 2013 “Assessment” paper and our 2008 “Target CO₂” paper[4], because of relevance to the public and because I wanted it to be clear that the results were not just my analysis but those of an exceptional group of scientists.

However, I felt that by continuing to push on the title in a potentially time consuming indirect interaction with the editorial board, relations could deteriorate as they had with the anonymous editorial board member at PNAS and publication was already delayed. Given the urgency of getting the paper out for the court case, when I was told to change “is dangerous” to “could be dangerous” in the title, I agreed to that. That title is disappointing, because “could be dangerous” is a conclusion that can be reached with little or no research.

The editor, who himself may have been becoming frustrated with the process of interacting with the editorial board, noted that he had only instructed me to change the statement that 2°C global warming “would be” dangerous to “could be” in the title, although he also noted that there would be an inconsistency if I left it as “would be” in the abstract. I did not want to raise a flag that could result in further delay or threaten publication, so I wrote “could be” in the abstract as well.

It seems to me that scientific reticence is now greater than when I first wrote on the topic.[5]^,[6],1 Do the public, policymakers, and courts understand that scientists use the word “dangerous” with a different meaning than that in the dictionary?  Did the Framework Convention not mean the common dictionary definition of the word?  In the “dark street” analogy, a person does not need to conclude with certainty that he would be killed on that street to conclude that it is dangerous.

Inertia of the climate system reduces present climate impacts, but it also makes it difficult to stop larger ones in decades ahead. Inertia in our energy systems implies that it takes decades to make major changes in emissions and atmospheric composition.  Because of the combination of these two slow systems, we are in danger of passing points of no return, such that we hand young people a climate system with great consequences, including the potential for large sea level rise and shutdown of the ocean’s overturning circulations, consequences that could be locked in soon if we do not reduce global emissions rapidly.

Scientific reticence is dangerous, and wrong in my opinion. I will return to that subject soon.
One final comment, closely related to scientific reticence. A criticism of our paper that may warrant response is that the ice melt rates that we assumed were “unrealistic”.  In fact it is certain that multi-meter per century melt rates have occurred many times in Earth’s history, spurred by much weaker forcings than the human-made forcing.  We presented evidence in our paper that rapid sea level rise even occurred in late-Eemian, when there was less ice available for melt than today.  Just this week a paper was published showing that the fastest natural increase of greenhouse gas climate forcing in the past 66 million years was at least 10 times slower than the human-made change[7].  Unfortunately, the melt rates we talk about for the next several decades are very realistic, and we are already seeing expected response to current melt rates.
 
References:

[1] Hansen, J.E., 2007: Scientific reticence and sea level rise. Environ. Res. Lett., 2, 024002, doi:10.1088/1748-9326/2/2/024002.
[2] Hansen, J., M. Sato, P. Hearty, R. Ruedy, M. Kelley, V. Masson-Delmotte, G. Russell, G. Tselioudis, J. Cao, E. Rignot, I. Velicogna, B. Tormey, B. Donovan, E. Kandiano, K. von Schuckmann, P. Kharecha, A.N. LeGrande, M. Bauer, and K.-W. Lo, 2016: Ice melt, sea level rise and superstorms: Evidence from paleoclimate data, climate modeling, and modern observations that 2°C global warming could be dangerous. Atmos. Chem. Phys., 16, 3761-3812, doi:10.5194/acp-16-3761-2016.
[3] Hansen, J., P. Kharecha, M. Sato, V. Masson-Delmotte, F. Ackerman, D. Beerling, P.J. Hearty, O. Hoegh-Guldberg, S.-L. Hsu, C. Parmesan, J. Rockstrom, E.J. Rohling, J. Sachs, P. Smith, K. Steffen, L. Van Susteren, K. von Schuckmann, and J.C. Zachos, 2013: Assessing “dangerous climate change”: Required reduction of carbon emissions to protect young people, future generations and nature. PLOS ONE, 8, e81648, doi:10.1371/journal.pone.0081648.
[4] Hansen, J., M. Sato, P. Kharecha, D. Beerling, R. Berner, V. Masson-Delmotte, M. Pagani, M. Raymo, D.L. Royer, and J.C. Zachos, 2008: Target atmospheric CO₂: Where should humanity aim? Open Atmos. Sci. J., 2, 217-231, doi:10.2174/1874282300802010217.
[5] Hansen, J.E., 2005: A slippery slope: How much global warming constitutes “dangerous anthropogenic interference”? An editorial essay. Climatic Change, 68, 269-279, doi:10.1007/s10584-005-4135-0.
[6] Hansen, J., 2006: The threat to the planet. New York Rev. Books, 53, no. 12 (July 13, 2006), 12-16.
[7] Zeebe, R.E., Ridgwell, A. and Zachos, J.C.: Anthropogenic carbon release rate unprecedented during the past 66 million years, Nature Geosci., published online 21 March 2016, doi:10.1038/NGEO2681

Eight to Eighteen Decades Before Irreversible Planetary Catastrophe

Links are available to Dr. James Hansen's, (and co-authors), alarming new paper on climate change presenting findings suggesting a range of some eight to 18 decades before Earth reaches a point of no return, ("locked-in"), of catastrophic consequences caused by human beings' fossil-fuel energy systems' emitting gasses changing the atmosphere.

'Consequences include sea level rise of several meters, which we estimate would occur this century or at latest next century, if fossil fuel emissions continue at a high level. That would mean loss of all coastal cities, most of the world’s large cities and all their history. A more immediate threat is the likelihood of shutting down the oceans overturning circulations in the North Atlantic and Southern oceans. That’s where superstorms come in ... .'

Hansen's new paper is entitled Ice Melt, Sea Level Rise and Superstorms: The Threat of Irreparable Harm:

• Nineteen-page abbreviation of Ice Melt, Sea Level Rise and Superstorms: The Threat of Irreparable Harm, with links to media, full paper, and video included
• Final Paper
• Video Discussion
• Dr. Hansen’s webpage, communications, etc. 
• Justin Gillis' piece in the New York Times 
• Amelia Urry's piece in the Grist 

It is possible a massive change in the energy production systems on a global scale could alter the consequences, suggests the paper.

Ice Melt, Sea Level Rise and Superstorms: The Threat of Irreparable Harm

'Irreparable harm—questions pertain to how soon we will pass points of no return, in which we lock in consequences that cannot be reversed on any time scale that people care about. Consequences include sea level rise of several meters, which we estimate would occur this century or at latest next century, if fossil fuel emissions continue at a high level. That would mean loss of all coastal cities, most of the world’s large cities and all their history. A more immediate threat is the likelihood of shutting down the oceans overturning circulations in the North Atlantic and Southern oceans. That’s where superstorms come in ... .'

It would perhaps be gratifying if the United States government began an emergency crash project on changing public policy related to the energy extraction industry, as if the species and biosphere depended on it.

A new paper by Dr. James Hansen and 18 co-authors reveals findings confirming precisely that, (Ice Melt, Sea Level Rise and Superstorms: The Threat of Irreparable Harm).

So we have the grave planetary situation facing the world, and in the United States the Republican Party busily demonizing not the energy extraction industries but rather the human species who appear non-white and hold to disfavored religious beliefs, while Hillary Clinton acclaims how tough she is in an address to AIPAC. [By the way, consider voting for Bernie Sanders for a dose of sanity.]

An excerpt and video of Hansen's talk laying out the main points of the paper are below. For some other reading explaining the consequences of inaction, see The Sixth Extinction, An Unnatural History by Elizabeth Kolbert (Henry Holt and Company (2014)).

Ice Melt, Sea Level Rise and Superstorms: The Threat of Irreparable Harm

22 March 2016

James Hansen

We made a video discussing some of the main points in our “Ice Melt” paper[1], which is about to be published in Atmos. Phys. Chem.

The main point that I want to make concerns the threat of irreparable harm, which I feel we have not communicated well enough to people who most need to know, the public and policymakers. I’m not sure how we can do that better, but I comment on it at the end of this transcript.

Hi, I’m Jim Hansen, Director of the Climate Science, Awareness and Solutions program at Columbia University Earth Institute. I want to discuss some implications of the paper Ice Melt, Sea Level Rise and Superstorms that is being published in Atmospheric Chemistry and Physics, a paper on which I have 18 exceptional American and international co-authors.

We have uncovered information and a partial understanding of feedbacks in the climate system, specifically interactions between the ocean and the ice sheets. These feedbacks raise questions about how soon we will pass points of no return, in which we lock in consequences that cannot be reversed on any time scale that people care about.

Consequences include sea level rise of several meters, which we estimate would occur this century or at latest next century, if fossil fuel emissions continue at a high level. That would mean loss of all coastal cities, most of the world’s large cities and all their history.

A more immediate threat is the likelihood of shutting down the oceans overturning circulations in the North Atlantic and Southern oceans. That’s where superstorms come in.  Let me explain.

We use global climate modeling, paleoclimate data – that’s Earth’s ancient climate history – and modern observations of the ocean and ice sheets to study effects of ice melt on Greenland [2] and the Antarctic ice shelves (tongues of ice extending from Antarctica into the Southern Ocean).[3]

Greenland and Antarctica are beginning to melt because of global warming. So far it is just a tiny, tiny fraction of the ice sheets that has melted. However, this fresh meltwater spilling out onto the North Atlantic and into the Southern Ocean already is having important effects. [F16]

We conclude that light freshwater added to upper layers of the ocean is already beginning to shut down North Atlantic Deep Water formation and Antarctic Bottom Water formation. This will have enormous consequences in future decades, if full shutdown is allowed to occur.

United Nations IPCC, Intergovernmental Panel on Climate Change, does not report these effects, for two reasons. First, most models used by IPCC simply exclude ice melt. Second, we conclude that most models, ours included, are less sensitive than the real world to added freshwater, because most models have excessive small scale ocean mixing, which reduces the effect.

[4] The surface manifestation of slowdown of the deep circulations is cooling in the North Atlantic southeast of Greenland and in the Southern Ocean. These coolings are prominent in our model by the middle of the 21st century.  However, on multiple grounds, we conclude that the real world responds faster to freshwater than the models do.

First, let’s note that North Atlantic cooling, if the overturning circulation shuts down entirely, will have large effects. The tropics continue to warm as CO2 increases. If Greenland freshwater shuts down deepwater formation and cools the North Atlantic several degrees, the increased horizontal temperature gradient will drive superstorms stronger than any in modern times.  All hell would break loose in the North Atlantic and neighboring lands.

[5 1st boulder] Such a situation occurred in the last interglacial period, 118 thousand years ago. The tropics were about 1°C warmer than today because Earth’s spin axis was tilted less than today.  Ocean core data show that deepwater formation shut down, the North Atlantic cooled, and there is evidence of powerful superstorms at about that time, powerful enough for giant waves to toss 1000 ton megaboulders [6] onto the shore in the Bahamas.  Some scientists think these boulders may have been tossed by a tsunami, but we present multiple lines of evidence that the boulders and other geologic features are best explained as the result of superstorms.

An important point is that if we let ice melt from Greenland become large enough to fully shut down the AMOC, the Atlantic overturning circulation, it will be permanent as far as the public is concerned. It takes several centuries for AMOC (Atlantic overturning circulation) to get moving again.

However, superstorms will not be the most important consequence of global warming, if it continues to grow. The most important effect will be sea level rise.  Here too, the most complete analysis must account for paleoclimate data, which shows that ice sheets, when they disintegrate, can go quickly, non-linearly, yielding multi-meter sea level rise in a century, even when the climate forcing is weaker than the human-made climate forcing.

[7] We show from paleoclimate data that most ice sheet models are more lethargic than the real world, in which sea level is known to have risen rapidly many times. So instead of using an ice sheet model, we simply assume that when warming occurs driven by a growing climate forcing the rate of ice melt will grow nonlinearly.  We test several alternative growth rates.

What we find are amplifying feedbacks, just what is needed to feed nonlinear ice melt growth. Greenland meltwater reduces the density of surface water, thus reduces sinking of water to the deep ocean.  As meltwater grows it shuts down the ocean conveyor, as Wally Broecker calls it.

More important, for sea level, is what is happening around Antarctica. Sinking of heavy, salty cold water near the Antarctic coast normally forms Antarctic Bottom Water, thus also bringing relatively warm water to the surface, where it releases heat to the atmosphere and space.

Now, as fresh meltwater from Antarctic ice shelves increases, it tends to put a cold low density lid on the Southern Ocean. This reduces exchange with the surface, so he heat stays in the ocean, raising the temperature of ocean water at the depth of ice shelves, an amplifying feedback.

In a global perspective, cold freshwater lenses around Antarctica increase the planet’s energy imbalance. The added energy goes into the ocean where it is available to melt ice shelves.

These feedbacks support our conclusion that melt in response to strong forcing will be nonlinear. These feedbacks, with meltwater driving subsurface warming, also help us understand and gain a consistent picture of rapid nonlinear climate oscillations in the paleoclimate record.

[8] Paleoclimate data makes clear that when ice sheets melt, they can go fast. However, we do not know the characteristic time for the nonlinear ice sheet response to growing climate forcing.  Eventually ice sheet models may give us an answer, but for now our best guide is observations.

Unfortunately records of growing annual mass loss by the ice sheets are short. The Greenland data can be fit as well by 10-year or 20-year doubling times, but already Greenland is losing several hundred cubic kilometers of ice per year.  Feedbacks for Greenland, with its surface melt, are different than for Antarctica, but there are several amplifying feedbacks.  Greenland response to global warming will be nonlinear, but likely with a different characteristic doubling time.

[9] Antarctic mass loss is smaller. Most melting so far is ice shelves, which does not show up in gravity satellite measurements of mass change.  However, as ice shelves disappear, the discharge of non-floating ice will accelerate.

If ice sheet mass loss has a 10-year doubling time, meter-scale sea level rise would be reached in about 50 years, and multi-meter sea level rise a decade later. 20-year doubling time would require about 100 years.

The data records are too short. But if we wait until the real world reveals itself clearly, it may be too late to avoid sea level rise of several meters and loss of all coastal cities.  I doubt that we have passed a point of no return, but frankly we are not certain of that.

[10] There’s an analogous, but I believe more imminent, situation with shutdown of overturning ocean circulations. The cold regions southeast of Greenland and around Antarctica are signs of the beginning of shutdowns of the AMOC, in the North Atlantic, and the southern Ocean SMOC.

We note that effects of meltwater seem to be occurring 1 or 2 decades earlier in the real world than in our model. Why would models be less sensitive to today’s moderate meltwater amounts? We present evidence for excessive small scale ocean mixing in many models, including ours.

[11] One key diagnostic is the climate response time. In 100 years our model achieves only 60% of its equilibrium response.  I have checked three other major climate models, two American and one British, finding similar slow response.  However, we have shown that Earth’s measured energy imbalance requires the 100-year climate response to be about 75% if equilibrium climate sensitivity is about 3°C, as paleoclimate data show to be the case.

The explanation for why the surface response is so slow in the model is that the model ocean mixes heat too rapidly into the deeper ocean. This same excessive mixing causes the models to be less sensitive to the freshwater lens on the ocean surface, which also tends to mix too fast.

There is other data, besides Earth’s energy imbalance, supporting this interpretation, including the sensitivity of paleoclimate to freshwater forcing. However, there is one recent paper that is especially important, by Winton et al. (2014), who show that a model with 0.1° resolution, fine enough to resolve small scale ocean motions and avoid parameterized mixing, yields a surface temperature response about a quarter larger after 50-100 years, consistent with our interpretation.

It would be valuable if all models would report their surface climate response function as well as their equilibrium climate sensitivity, and examine the model sensitivity to a standard rapidly increasing rate of meltwater injection. [4]

The relevance is that I believe we are already witnessing the beginning of this cooling southeast of Greenland and cooling around Antarctica in response to freshwater from ice melt.

[10] In that case observed cooling southeast of Greenland and the extra warming along the United States East Coast are not natural fluctuations – when AMOC slows down it causes both of those. This interpretation implies that Greenland meltwater is already having significant effects.  The warm water along the East Coast is the reason that “Sandy” retained hurricane force winds all the way up to the New York City area – the nearby Atlantic was about 3°C warmer than normal.  This unusually warm ocean water has also been able to provide the moisture for record snowstorms in recent years.

These are small effects compared to what happens if AMOC shuts down entirely.

So the question arises again: have we passed a point of no return, is ice melt sure to increase so that AMOC shutdown is a foregone conclusion? I doubt it, but it’s conceivable, depending on how fast we slow down human-made climate forcing.

I think the conclusion is clear. We are in a position of potentially causing irreparable harm to our children, grandchildren and future generations.

This is a tragic situation – because it is unnecessary. We could already be phasing out fossil fuel emissions if only we stopped allowing the fossil fuel industry to use the atmosphere as a free dumping ground for their waste. If we collected a gradually rising fee from fossil fuel companies, we could phase over to clean energies – if done right it would spur the economy and create jobs.

But that’s a story for another day.

One final point. This is a complex story, but one with important practical implications.  I find that the public sometimes misinterprets our science discussions, how research is done.  Skepticism is the lifeblood of science.  You can be sure that many scientists, indeed most scientists, will find some aspects in our long paper that they would interpret differently.  That’s entirely normal.  It takes time for conclusions to be agreed upon and details sorted out.

So after you have talked to a scientist about this topic, ask him or her a final question. Do you agree that we have reached a dangerous situation?  Do you think we may be approaching a point of no return, a situation in which our children inherit a climate system undergoing changes that are out of their control, changes that will cause them irreparable harm? That’s the bottom line.

Thanks for listening.

[1] Hansen, J., M. Sato, P. Hearty, R. Ruedy, M. Kelley, V. Masson-Delmotte, G. Russell, G. Tselioudis, J. Cao, E. Rignot, I. Velicogna, E. Kandiano, K. von Schuckmann, P. Kharecha, A.N. LeGrande, M. Bauer, and K.-W. Lo, 2016: Ice melt, sea level rise and superstorms: Evidence for paleoclimate dat, climate modeling, and modern observations that 2°C global warming could be dangerous.. Atmos. Chem. Phys., in press.