An introduction to global warming impacts: Hell and High Water

In this post, I will summarize what the recent scientific literature says are the key impacts we face in the second half of the century if we stay anywhere near our current emissions path. I will focus primarily on:

  • Staggeringly high temperature rise, especially over land — some 10°F over much of the United States
  • Sea level rise of 3 to 7 feet, rising some 6 to 12 inches (or more) each decade thereafter
  • Dust Bowls over the U.S. SW and many other heavily populated regions around the globe
  • Massive species loss on land and sea — 50% or more of all life
  • Unexpected impacts — the fearsome “unknown unknowns”
  • More severe hurricanes — especially in the Gulf

Equally tragic, a 2009 NOAA-led study found the worst impacts would be “largely irreversible for 1000 years.”

The single biggest failure of messaging by climate scientists (until very recently) has been the failure to explain to the public, opinion makers, and the media that business-as-usual warming results in impacts that are beyond catastrophic. For these impacts, terms like “global warming” and “climate change” are essentially euphemisms. That is why I prefer the term “Hell and High Water.”

Business-as-usual typically means continuing at recent growth rates of carbon dioxide emissions, which we now know would take us to atmospheric concentrations of carbon dioxide greater than 1000 ppm (see U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories (or even worse) are being realised” — 1000 ppm). We are at about 8.5 billion metric tons of carbon a year (GtC/yr) and, until the recent global economic recession, were rising about 3% per year.

What is less well understood is that even a very strong mitigation effort that kept carbon emissions this century to 11 GtC a year on average would still probably take us to 1000 ppm — a little noted conclusion of the 2007 Intergovernmental Panel on Climate Change (IPCC) report (see “Nature publishes my climate analysis and solution“).

The scientific community has spent little time modeling the impacts of a tripling (~830 ppm) or quadrupling (~1100 ppm) carbon dioxide concentrations from preindustrial levels. In part, I think, that’s because they never believed humanity would be so stupid as to ignore the warnings and simply continue on its self-destructive path. In part, they lowballed the difficult-to-model amplifying feedbacks in the carbon cycle.

So I pieced together those impacts from available studies and from discussions with leading climate scientists for my book, Hell and High Water. But now as climate scientists have sobered up to their painful role as modern-day Cassandra’s, the scientific literature on what we face is much richer. Let me review it here.


Two of the best recent analyses of what we are headed towards can be found here:

As Dr. Vicky Pope, Head of Climate Change Advice for the Met Office’s Hadley Centre explains on their website (here):

Contrast that with a world where no action is taken to curb global warming. Then, temperatures are likely to rise by 5.5 °C and could rise as high as 7 °C above pre-industrial values by the end of the century.

That likely rise corresponds to roughly 9°F globally and typically 40% higher than that over inland mid-latitudes (i.e. much of this country) — or well over 10°F.

[Note:  The MIT rise is compared to 1980-1999 levels see study here).  So you can add at least 0.5 C and 1.0°F for comparison with pre-industrial temperatures.]

Based on two studies in the last few years:

By century’s end, extreme temperatures of up to 122°F would threaten most of the central, southern, and western U.S. Even worse, Houston and Washington, DC could experience temperatures exceeding 98°F for some 60 days a year. Much of Arizona would be subjected to temperatures of 105°F or more for 98 days out of the year–14 full weeks.

Yet that conclusion is based on studies of only 700 ppm and 850 ppm, so it could get much hotter than that.

And the Hadley Center adds, “By the 2090s close to one-fifth of the world’s population will be exposed to ozone levels well above the World Health Organization recommended safe-health level.”

The Hadley Center has a huge but useful figure which I will reproduce here:


A 5.5°C warming would likely lead to the mid- to high-range of currently projected sea level rise — 5 feet or more by 2100, followed by 10 to 20 inches a decade for centuries. The best recent study is

Needless to say, a sea level rise of one meter by 2100 would be an unmitigated catastrophe for the planet, even if sea levels didn’t keep rising several inches a decade for centuries, which they inevitably would. The first meter of SLR would flood 17% of Bangladesh, displacing tens of millions of people, and reducing its rice-farming land by 50 percent. Globally, it would create more than 100 million environmental refugees and inundate over 13,000 square miles of this country. Southern Louisiana and South Florida would inevitably be abandoned. And salt water infiltration will only compound this impact (see “Rising sea salinates India’s Ganges“). As will hurricanes (see below).

The scientific literature has been moving in this direction for a couple of years now — too late for the IPCC to consider in its latest assessment. For instance, an important Science article from 2007 used empirical data from last century to project that sea levels could be up to 5 feet higher in 2100 and rising 6 inches a decade (see Inundated with Information on Sea Level Rise)!

Another 2007 study from Nature Geoscience came to the same conclusion (see “Sea levels may rise 5 feet by 2100“). Leading experts in the field have a similar view (see “Amazing AP article on sea level rise” and “Report from AGU meeting: One meter sea level rise by 2100 “very likely” even if warming stops?“).

Note: Since global warming deniers and delayers like to hide behind the IPCC’s 2007 sea level estimate — even though they really don’t believe most of what the IPCC says or most of the scientific literature on which it bases its conclusion — you’re going to be hearing the IPCC estimate for another several years, until the IPCC does a new report and puts in a more realistic estimate. That said, while the delayers never acknowledge it, even the 2007 IPCC report “was the first to acknowledge that the melting of the Greenland ice sheet from rising temperature [which would raise the oceans 23 feet] could result in sea-level rise over centuries rather than millennia,” as the NYT put it (see “Absolute MUST Read IPCC Report: Debate over, further delay fatal, action not costly“).

Yet even a major report signed off on by the Bush administration itself was forced to concede that the IPCC numbers are simply too out of date to be quoted anymore:


Then we have moderate drought over half the planet, plus the loss of all inland glaciers that provide water to a billion people.

The unexpectedly rapid expansion of the tropical belt constitutes yet another signal that climate change is occurring sooner than expected,” noted one climate researcher in December 2007. A 2008 study led by NOAA noted, “A poleward expansion of the tropics is likely to bring even drier conditions to” the U.S. Southwest, Mexico, Australia and parts of Africa and South America.”

In 2007, Science (subs. req’d) published research that “predicted a permanent drought by 2050 throughout the Southwest” — levels of aridity comparable to the 1930s Dust Bowl would stretch from Kansas to California. And they were only looking at a 720 ppm case! The Dust Bowl was a sustained decrease in soil moisture of about 15% (“which is calculated by subtracting evaporation from precipitation”).

A NOAA-led study similary found permanent Dust Bowls in Southwest and around the globe on our current emissions trajectory (and irreversibly so for 1000 years). And as I have discussed, future droughts will be fundamentally different from all previous droughts that humanity has experienced because they will be very hot weather droughts (see Must-have PPT: The “global-change-type drought” and the future of extreme weather).

I should note that even the “moderate drought over half the planet”³ scenario from the Hadley Center is only based on 850 ppm (in 2100). Princeton has done an analysis on “Century-scale change in water availability: CO2-quadrupling experiment,” which is to say 1100 ppm. The grim result: Most of the South and Southwest ultimately sees a 20% to 50% (!) decline in soil moisture.


In 2007, the IPCC warned that as global average temperature increase exceeds about 3.5°C [relative to 1980 to 1999], model projections suggest significant extinctions (40-70% of species assessed) around the globe. That is a temperature rise over pre-industrial levels of a bit more than 4.0°C. So a 5.5°C rise would likely put extinctions beyond the high end of that range.

And, of course, “When CO2 levels in the atmosphere reach about 500 parts per million, you put calcification out of business in the oceans.” There aren’t many studies of what happens to the oceans as we get toward 800 to 1000 ppm, but it appears likely that much of the world’s oceans, especially in the southern hemisphere, become inhospitable to many forms of marine life. A 2005 Nature study concluded these “detrimental” conditions “could develop within decades, not centuries as suggested previously.”

A 2009 study in Nature Geoscience warned that global warming may create “dead zones” in the ocean that would be devoid of fish and seafood and endure for up to two millennia (see Ocean dead zones to expand, “remain for thousands of years”).

A 2010 Nature Geoscience study found that Oceans are acidifying 10 times faster today than 55 million years ago when a mass extinction of marine species occurred.


If we go to 800 ppm — let alone 1000 ppm or higher — we are far outside the bounds of simple linear projection. Some of the worst impacts may not be obvious — and there may be unexpected negative synergies. The best evidence that will happen is the fact that it is already happened with even a small amount of warming we have seen to date.

“The pine beetle infestation is the first major climate change crisis in Canada” notes Doug McArthur, a professor at Simon Fraser University in Vancouver. The pests areprojected to kill 80 per cent of merchantable and susceptible lodgepole pine” in parts of British Columbia within 10 years — and that’s why the harvest levels in the region have been “increased significantly.”

As quantified in the journal Nature, “Mountain pine beetle and forest carbon feedback to climate change,” (subs. req’d), which just looks at the current and future impact from the beetle’s warming-driven devastation in British Columbia:

the cumulative impact of the beetle outbreak in the affected region during 2000–2020 will be 270 megatonnes (Mt) carbon (or 36 g carbon m-2 yr-1 on average over 374,000 km2 of forest). This impact converted the forest from a small net carbon sink to a large net carbon source.

No wonder the carbon sinks are saturating faster than we thought (see here) — unmodeled impacts of climate change are destroying them:

Insect outbreaks such as this represent an important mechanism by which climate change may undermine the ability of northern forests to take up and store atmospheric carbon, and such impacts should be accounted for in large-scale modelling analyses.

And the bark beetle is slamming the Western U.S. and Alaska, too (see “Oldest Utah newspaper: Bark-beetle driven wildfires are a vicious climate cycle“).

The key point is this catastrophic climate change impact and its carbon-cycle feedback were not foreseen even a decade ago — which suggests future climate impacts will bring other equally unpleasant surprises, especially as we continue on our path of no resistance.


Even if we don’t see an increase in the worst hurricanes hurricanes, the rising sea levels alone would put a growing number of coastal cities below sea level. Such cities are particularly hard to protect from major hurricanes as we saw with New Orleans. And that suggests in the second half of this century, we will be increasingly reluctant to rebuild cities devastated by major hurricanes.

That said, the literature suggests we will see an increase in severe hurricanes (see “ Hurricanes ARE getting fiercer — and it’s going to get much worse“). A 2008 Nature studied concluded:

The team calculates that a 1 ºC increase in sea-surface temperatures would result in a 31% increase in the global frequency of category 4 and 5 storms per year: from 13 of those storms to 17. Since 1970, the tropical oceans have warmed on average by around 0.5 ºC. Computer models suggest they may warm by a further 2 ºC by 2100.

Well, actually, those are the old computer models running old scenarios of emissions without much consideration of amplifying carbon cycle feedbacks. On our current emissions path, key parts of the tropical oceans are likely to warm considerably more than 2°C by century’s end.

For a longer discussion of why future hurricanes in the Gulf of Mexico are likely to become far more dangerous in the future, see (Why global warming means killer storms worse than Katrina and Gustav, Part 1 and Part 2).


We can’t let this happen. We must pay any price or bear any burden to stop it.

And let me make one final point. I think it is increasinly clear the “middle ground” scenarios are unstable in that once you hit 500 ppm (or possibly lower), the amplifying feedbacks kick in: These feedbacks include:

As Dr. Pope puts it, “If the climate turns out to be particularly sensitive to increases in greenhouse gases and the Earth’s biological systems cannot absorb very much carbon then temperature rises could be even higher.”

Indeed, some of the best research on this has come from the Hadley Center, since it has one of the few models that incorporates many of the major carbon cycle feedbacks. In a 2003 Geophysical Research Letters (subs. req’d) paper, “Strong carbon cycle feedbacks in a climate model with interactive CO2 and sulphate aerosols,” the Hadley Center, the U.K.’s official center for climate change research, finds that the world would hit 1000 ppm in 2100 even in a scenario that, absent those feedbacks, we would only have hit 700 ppm in 2100. I would note that the Hadley Center, though more inclusive of carbon cycle feedbacks than most other models, still does not model most of the feedbacks above or any feedbacks from the melting of the tundra even though it is probably the most serious of those amplifying feedbacks.

So we must stabilize at 450 ppm or below — or risk what can only be called humanity’s self-destruction. Since the cost is maybe 0.11% of GDP per year — or probably a bit higher than that if we shoot for 350 ppm — the choice would seem clear. Now if only the scientific community and environmentalists and progressives could start articulating this reality cogently.


61 Responses to An introduction to global warming impacts: Hell and High Water

  1. paulm says:

    Ocean acidification is an open ended one also. We don’t know how soon this will start to impact the food chain.

  2. Joe, what a superb summary. As change progresses, I would hope this can be an annual summary, or more often. Thanks.

  3. Sasparilla says:

    Great summary Joe, thanks for putting it up.

  4. It is an impressive summary, thank you! What’s even more frightening is that you’ve omitted some of the recent studies summarized at the recent climate congress in Copenhagen, including a Hadley paper suggesting that we’ll have an 85 percent mortality rate in the Amazon rainforest with just 4°C warming.

    We have to fight to save this planet.

  5. Anthony, rabid doomsayer says:

    Joe’s summary as bad as it sounds is not the worst of the predictions. North to Alaska, by 2100 (or soon after) it should have a nice Florida climate.

    The cull of humans this century is going to be horrific.

  6. Dorothy says:

    Richard, thank you for calling attention to the March Copenhagen Climate Congress. The six ‘key messages’ ( were indeed strongly worded. However, we’ve just posted a transcript of the Closing Plenary Session, which you will find pretty disheartening. See the article at The conclusions of 2000 climate scientists are being politicized almost immediately, on the last day of the conference, and this doesn’t bode well for the December Copenhagen meeting, nor for any of us poor humans.

    Thanks also to Joe for this useful article. We’re going to put the permalink to it on our West Coast Climate Equity website.

  7. ecostew says:

    A few more:

    Many glacial “reservoirs” of fresh water (which provide freshwater to millions of us & don’t forget the ecosystem) are quickly loosing their ability to provide a most precious resource.

    The increase in temperature & associated E/ET rates associated with AGW will diminish crop yields within a couple of decades. Pollination/growth is a huge issue.

    The annual flow hydrographs of river basins are changing. The 30-year current-planning approach does not work.

    Ecosystems are changing!

    However, we must never loose track of our energy security!

  8. Just after reading this post, I watched a one hour documentary called Global Warming: The New Challenge with Tom Brokaw. The cable channel is PLGN or Planet Green. It focuses on effects from global warming that we are seeing now, and how it is already effecting humans. So we have at least one major news anchorman who gets it. It would be good to see this on something other than Planet Green, like major networks at prime time.

  9. The documentary mentioned above is being shown again at
    9 PM PDT. The second half hour is about solutions.

  10. paulm says:

    …”Hey, it’s only a movie! Right?”

    Here comes 1984!

    Does this mean we now have enough time to save the planet now?

  11. Joe, thanks a very useful summary.

    You implicitly talk in ppm CO2 but it would be useful in a post like this if you linked to an explanation of the difference between CO2 and CO2e targets. As you know, the IPCC and most governments are working on targets based on CO2e.

    I can’t recall seeing one of your own posts on this topic, but I presume you have one. A couple of links to other websites for this issue are and

  12. paulm says:

    Here’s Hansen being interview by the Guardian……Hansen ahead of the curve. What he said ten years ago, we now recognize as happening. What he says now will be reality in five or so years time!

    Science Weekly: Meet the mind-reader

    There are no governments anywhere who are prepared to implement the required action to save the planet. Japan, UK etc are all still Greenwash.

    Hansen, says the only way to reduce our CO2 on the level required in the time required is a Carbon tax. This is probably the only hope we have. It means an extension to the depression though of course.

  13. Joe B says:

    Joe, species collapse will be a chain effect that will make it impossible to render food and safety for even 1 billion people. Read Plagues and Peoples and you’ll start including a lot more about catastrophic new disease vectors as an EARLY result of everything you refer to.

  14. Harrier says:

    I’m surprised Joe hasn’t done a post about this, or at least hasn’t done a Peak Oil post recently.

    According to the folks at The Oil Drum, we hit Peak Oil some time between 2004 and 2008. It’s all downhill from hereon out. We’re going to have a rather drastic reduction in emissions as we run out of petroleum to burn.

  15. Bob Wallace says:

    Good, good, good…

    May I suggest two things:

    1) Put the some high impact, attention getting stuff at the very beginning. For example:

    By century’s end, extreme temperatures of up to 122°F would threaten most of the central, southern, and western U.S. Even worse, Houston and Washington, DC could experience temperatures exceeding 98°F for some 60 days a year. Much of Arizona would be subjected to temperatures of 105°F or more for 98 days out of the year–14 full weeks.

    Get the casual reader’s attention. Hit them where it hurts.

    Perhaps less about Bangladesh up top and more about New York and Miami going under.

    2) Create a “sticky zone” – say right under your book ad.

    Put some basic info about the sticky articles – that they will be updated periodically based on new information and in particular new information posted in their discussion areas.

    Bring your audience in and get them busy collecting more info for you.

    Include a “last updated” date in the sticky zone so that people can judge whether or not the info is current.

  16. Bob Wallace says:

    Here’s a site that had a big impact on me.

    You might take a look at this as a way to get people’s attention.

  17. Harrier says:

    What makes me uneasy is wondering where the climate might finally stabilize. Let’s say that, by a combination of voluntary and involuntary pressures, we do stop emitting greenhouse gases in mass quantities by about 2050. We know we’ll be in for more warming after that, but it’s also the case that the Earth has been uniformly warmer in the past than it is today for millions of years at a time.

    I’ve read about the positive feedbacks, but at what temperature could the global climate stabilize again once we’ve eliminated our emissions?

  18. Bob Wallace says:

    Harrier – from the Six Steps to Hell page…

    “Scientists estimate that we have at best 10 years to bring down global carbon emissions if we are to stabilise world temperatures within two degrees of their present levels. The impacts of two degrees warming are bad enough, but far worse is in store if emissions continue to rise. Most importantly, 3C may be the “tipping point” where global warming could run out of control, leaving us powerless to intervene as planetary temperatures soar.”

    The site describes a 2 degree warmer world.

    (And do read the description of a +6 degree world.)

    Perhaps Joe can take a look at that two year old site and see if the information is accurate/current.

  19. paulm says:

    Bob good link.

    What has not been highlighted is the cumulative effect of all this! We talk about 1°C & 2°C events as if they are standalone. The problem is its started now and the deterioration is just going to aggregate.

    A few examples….
    *Katrina – New Orleans will never be the same. Huston will be hit again in the next couple of years and will be struggling. US Oil supply is going to tank.

    *Cuba, Haiti, many Caribbean Islands – one more season like last years and their societies will be crippled and wont probably recover before the next event. This is likely in the next couple of years.

    *California, Australia & Greece – the ongoing fires and droughts are just going to get worse and their economies are going to start to collapse from now.

    I am afraid we are heading for chaos and collapse within the next 10 – 15yrs.

    (Price of food staples seems to be going up again – could there be a link to CO2 emissions?)

  20. Harrier says:

    Bob, I did read the Six Steps to Hell page, and I’ve read a few other sites and graphics that depict similar scales of warming and their effects. I’m still wondering where it all might stop. How far might runaway global warming ‘runaway’ to, exactly?

    James Lovelock thinks we might head for something similar to the Palaeocene-Eocene Thermal Maximum.

  21. paulm says:

    lts the Nano!
    ‘People’s car’ Nano to go on sale in India

    Say goodbye to India meeting its emissions target and Hybrids ….

  22. Bob Wallace says:

    I wonder about the impact of the Nano.

    From my experience in India, the Nano is going to replace a bunch of motor scoters (often with 2,3, 4 riders) and some very polluting public buses.

    A quick look on the web says that Vespa scooters get from 50 to 70 mpg and Nanos get 50 mpg.

    Might not be an appreciable change….

    (Tato is still saying that they will bring the Tato Air Car to market in the next couple of years. That will help lower emissions as they also bring more wind and solar to their grid.)

  23. Bob Wallace says:

    A word about these “stickies”….

    Perhaps we should make a concerted effort to stay on topic. (I realize that I just violated that rule.)

    If we want Joe to read, digest, and incorporate our inputs we should make his job as easy as possible.

  24. Ike Solem says:

    Unfortunately, the time for prevention is over – we are committed to at least five decades of warming at current rates, with uncertainties – for example, a gigantic volcanic eruption could slow the warming for a decade, perhaps, but that would only result in faster warming later. Ocean heat content is the real metric to watch, as it takes decades to equilibrate with the atmosphere.

    Given the biological and permafrost feedbacks involved, it appears that even if fossil fuel emissions were halted tonight, CO2 levels would still gradually rise as drought and melting permafrost both resulted in the conversion of soil carbon and tree biomass to atmospheric CO2. The only plausible mechanisms for CO2 removal from the atmosphere are similar to those that formed fossil fuels in the first place – namely, mass burial of photosynthetically produced carbon, which would take hundreds of years at best.

    There is a fundamental need to adapt to a new climate regime that will be much less hospitable than in the past – as well as a fundamental need to entirely abandon the use of fossil fuel combustion as an energy source, starting with coal. To do that, we’ll need large-scale solar and wind and storage technology – which also have the great benefit of not requiring large supplies of water for daily operations, in contrast to all steam-turbine based technologies, from coal to nuclear.

    This will lead to fundamental changes in the global economic order, which is why there is so much resistance. It’s not a conservative or liberal issue – the greatest resistance to shutting down coal plants and replacing them with renewable systems is coming from coal-state Democrats in alliance with most Republicans, and the neoliberal position on tar sand oil is that global trade should not be subject to environmental restrictions – no different from the neoconservative position.

    The largest threats over the next fifty years – the unavoidable reality, rather than the long-term speculations – could be grouped as follows:

    1) Water shortages related to more frequent episodes of drought as well as steady loss of late-summer runoff from melting glaciers, particularly in the subtropical belts, roughly 15-45 degrees on either side of the equator. That affects both energy production and food production (see below).

    2) Food shortages related to water shortages, as well as to heat waves and other extreme weather events. Storms are generated as cold dry air mixes with warm wet air; in a warmer world, the continental interior atmosphere will be drier and the ocean atmosphere will be wetter, as modified by the global air circulation – but that will span more violent mid-latitude storms – crop loss figures will inevitably increase.

    3) High temperatures in some regions will make energy generation difficult – for example, during recent summer heat waves France has had to shut down nuclear reactors because the intake water was too warm.

    4) Loss of biodiversity appears to be continuing and even increasing, with global warming now appearing to be playing as big of a role as habitat destruction has in the past. We rely heavily on biological diversity for breeding crops – but that’s hardly the only reason to prevent the permanent loss of unique species.

    5) Increased global migration of both humans and our diseases, including malaria, west nile virus – the main concern is the increased winter ranges of insect vectors, as well as unknown levels of environmental refugees seeking stability.

    Those are the real dangers over the short term, and they revolve around the basics: water, food, energy and living space. Meeting those challenges alone will require a great deal of focused effort on the part of the public, government and business interests – but due to the huge role of fossil fuels in the global economy, it just isn’t happening on the necessary scale.

    One of the reasons is startling, and that is that renewables drive down the price of fossil fuels. The supply-demand equation for energy is a lot more sensitive to demand than previously thought, even in this era of “peak oil”. We’ve seen a 5% drop in consumer demand bring the price of oil (artificially inflated, true) down from $140 to $40 over a very short time period. One major goal of the economic stimulus effort is to raise the price of oil back to higher levels, thereby recouping much of the losses – but what will rapid, full-speed development of renewable energy do in the United States?

    It will probably send the price of oil through the floor, and once gigawatt-scale solar plants start replacing coal, that’ll be the end for that as well – and not for want of supply. The Stone Age did not end for want of stones, and the Fossil Fuel Age will not end for want of fossil fuels. Unfortunately, we inherited too much wealth in the form of buried energy-dense carbon molecules – because if we had run out fifty years ago, we’d already be running everything on solar and wind and photosynthesis.

  25. The 2 main threats are:
    .sea level rise
    .loss of moutain glaciers providind the fresh water during summer for agriculture and human drinking (remind Chu’s warning about the future of California).
    The mandatory (but not sufficient) solution: to put a price on carbon with a strong carbon taxe, starting at the end of the year (Copenhague meeting) and with redistribution.

  26. jorleh says:

    What about 2200? 2300? Or are we looking for some miracle to save us?

    Deniers are religious fundamentalists, they believe in miracles. Why don`t they believe in science? And they believe that science makes this miracle, just the science in which they don`t believe.

  27. Craig says:

    In reading this blog and other similar sources regarding the cost of mitigation, I frequently come across summaries of what would be required (for example, the ‘Princeton’ wedges). In aggregate, these seem like huge and costly undertakings.

    On the other hand, in the last paragraph of today’s blog, the cost is estimated at 0.11% of GDP (I’m thinking ‘per year’ is redundant, unless that’s part of my misunderstanding and what is meant is a cost which increases by 0.11% of GDP per year). This cost seems rather small and manageable.

    Certainly, these are both simply ‘gut feel’ observations — is my gut just not very well calibrated, or am I misunderstanding something?

  28. We’ve got to be united to save earth! Earth Hour is practised at large scale in all developed and developing countries but there has been more publicity and awareness this year, as well as participation from large corporations like which is a good sign – that there is still hope and that people still care!

    Let’s all do this, no matter where you are! Saturday, 28 March 2009. Lights off from 8.30pm to 9.30pm!

    Nature Concern

  29. Craig says:

    To Moderator: just a follow-up on my previous post, to provide my email address.

  30. CTF says:

    Really great summary–thanks.

  31. Craig says:

    I’m a layperson learning more about climate change — so, a question:

    Reading this blog and other similar sources, I frequently come across summaries of what might be required to mitigate climate change (for example, the ‘Stabilization Wedges’ from Pacala and Socolow). The solutions required seem like huge and costly undertakings.

    On the other hand, I commonly read statements like what is written in the final paragraph of today’s blog entry by Joseph Romm:

    “… the cost is maybe 0.11% of GDP per year — or probably a bit higher than that if we shoot for 350 ppm”

    This actually seems reasonably small and manageable for a problem of this global scope and severity (‘only’ 0.11% of GDP — granted that’s still a big number).

    Certainly, calling one ‘huge and costly’ and the other ‘small and manageable’ are simply gut level observations on my part — is my gut way out of calibration?

    Would implementing all of the stabilization wedges (or some similar aggregate solution) cost approximately 0.11% of GDP, or am I misunderstanding what is meant?

    [JR: This is a very good question, which I will be addressing in a couple of future posts, including one this week. But the short answer is that the absolute cost is roughly a 1% to 2% additional spending (i.e. a shift from non-energy spending) plus a shift in the planned energy-related spending ( from inefficient, polluting technologies towards efficient, low carbon technologies). That absolute additional cost, however, is not “lost” but rather represents an investment in technology, some of which pay for itself. The overall net reduction in GDP is according to the IPCC about 0.11% of GDP — but of course that doesn’t count the various non-economic benefits from reducing pollution, dependence on oil, and so on.]

  32. Misfortunately, you are correct.

  33. Roger says:

    Great summary, JR! OK, but what to do? I like Jim Hansen’s carbon tax.

    Let’s rally around the idea of a worldwide carbon tax to capitalize the coming social costs that Joe summarizes here. Here’s the math: take 0.11% of worldwide GDP and divide it by annual wordwide carbon production, as contained in fossil fuels. The result is the amount to be collected in dollars per ton of carbon for each fuel. Spend the collected funds on mitigation, education, etc. (Use a duty system for non taxers.)

    Adjustments will be needed, as price elasticity of demand impacts put downward pressure on carbon demand. But this is good: depending on the rates of change for GDP and carbon demand, it is quite possible that the carbon tax/ton will increase, further dampening carbon demand.

  34. Bob Wallace says:

    Shorter term problems: Drought, flash floods and earthquakes. All tied to glacier loss.

    Much of south Asia and parts of South America are dependent on gradual melt of winter snow melt for their water during the dry part of the year. As the glaciers melt and snow pack decreases dry season water is going to become critical for a billion plus people.

    During the melting period we are likely to see entire Himalayan villages wiped out as runoff lakes higher up the mountain overflow their natural dams and breach, sending large volumes of water down on people living on the slopes.

    And as we melt the glaciers we are going to be taking restraining loads off large areas, freeing them to move – think earthquakes (and possible tsunamis).

  35. Marie says:

    Does anyone have time to generate a list of citable references for Joe’s links and sources here?

  36. miha says:


    None of you seems to be bothered, that there is very weak correlation between CO2 and temperature and that in most cases higher temperature preceeds higher CO2 levels and not vice versa :-)

    And there is very strong correlation between sun activity and temperature,…

    But of course, eco-fanatics can not “regulate” and bully the Sun ;-)

    BR : Miha

    [JR: These are long debunked right wing talking points. In fact, more than a dozen major studies published in the last few years to make quite clear there is no correlation between sun activity and temperature in recent decades. And historically orbital changes trigger temperature increases that then cause carbon cycle feedbacks that cause the very rapid warming we see in the reconstructed temperature record. Today, it is humans who are acting as the initial prod, but the prospects for a very rapid warming from carbon cycle feedbacks are a genuine worry.]

  37. Ian Z says:

    So, miha: is it happening, or not? Why is it that people who oppose action never quite commit to answering this basic question? Do you believe if we do nothing, the kind of environmental and climatic change outlined above is coming, or not? There really isn’t much point in arguing with you & friends unless you answer this question straight.


  38. DavidCOG says:


    It would be great if you could stick to Celsius in your writing – it’s the scientific / international unit (you can always add Fahrenheit in brackets for your domestic viewers).

  39. Andrew says:

    Thanks for the quick rebuttal to the ‘sun is causing it’ comment. I really hate that tired old talking point.
    Our CO2 increase on its own isn’t the Primary driver, but it IS the trigger which started things off. The Earth would probably have gone through a natural temperature upswing over the next 50,000 yrs or so, but our little contribution ensures that it’ll happen NOW, in our lifetimes.

    And knowing human nature, both small-scale and political, my friends and I are moving back to Alaska and settling in for the long haul.

    Lovelock is dead on.

  40. Projected scenarios to the year 2100 are done just because it is a nice round number in a fairly distant future.

    More difficult are predictions for the 2050 range — a time when many reading this can expect to witness. This won’t be just half of 2100 but interesting because by then humans will be fully engaged in the chaos of change. And variously engaged in adaptations or mitigations.

    I would like to read more about interim scenarios.

  41. barbiplease says:

    I’m interested in knowing how the recent NASA study that attributes at least 45% or more of Arctic warming to aerosols (black carbon emissions) from industrial plants in China may impact mitigation efforts for CO2 reduction.

    The reason I ask is because I have noticed many denier sites that are citing this study to argue that “previous regulations on aerosols caused Arctic ice melt” and that “CO2 is not the main cause of global warming, according to NASA.”

    An excerpt from NASA article:

    “This is an important model study, raising lots of great questions that will need to be investigated with field research,” said Loretta Mickley, an atmospheric chemist from Harvard University, Cambridge, Mass. who was not directly involved in the research. Understanding how aerosols behave in the atmosphere is still very much a work-in-progress, she noted, and every model needs to be compared rigorously to real life observations. But the science behind Shindell’s results should be taken seriously.”

    I also have a question that I would like to pass along here posted by a reader of that NASA article, since I too was confused by the wording of the article:

    On Apr 10, 2009 11:00 AM Ron Broberg wrote:

    “This NASA article talks about 40 years of additional warming caused by removing sulfates (and their net cooling effect) from the atmosphere. But most speculation around Arctic warming has been about increasing BC aerosol from China. Increasing BC from China implies increased sulfates from China, unless China is employing sulfate scrubbers in their coal plants. So I’m a little confused about the sources and effects that this article is addressing.

    Any chance someone can clarify the CN -v- EU US sources, time lines, aerosol compositions, and effects. No doubt this is addressed in the paper, but a little extra detail here would be nice.”

    If anyone cares to address any of the questions above, please comment back.

    Here’s the link:

  42. lorna says:

    Great sharing of thoughts on impacts of Climate Change and technologies and adaptation/mitigation actions; but non on how to infect the social science aspect. This needs to be internalized and understood by politicians, media, educators, etc. and need to be translated into behavioral and mindsets of the manufacturers’ shops, homes, and classrooms. Business-as-usual mode in terms of use of nature’s resources, particularly for enterprising groups continues all throughout the world. Fortunately for developed countries, how about the developing countries who manufacture goods for the developed countries, without factoring in negative externalities to the manufacturing countries’ biodiversity and various ecosystems (forests, rivers, seas) where pollutants are likely to settle and destroy existing life forms.

  43. Joe says:

    Great summary… but couldyou please use metric numbers as well as US ones? Inches and fahrenheit don’t resonate with most international readers (except some older British ones).

  44. Die says:

    Last chance to give over our fear of mortality and lack, which has bought us to the brink of extinction. Time some other species ruled in a few thousand years or so once the dust settles. We are now the dinosaurs of the future. The planet Earth still has enough time to see the rise and fall of a few other dominant species before its inevitable death, its evolution however premature. I suppose the dinosaurs ran about confused and screaming when the changes came to.

  45. yoxx says:

    It is an impressive summary…

  46. Bianca says:

    This was a very informative summary. I never realized how bad we were making it for ourselves and the earth’s future inhabitants. This has definitely motivated me to take action and do whatever I can to contribute so that maybe, it won’t actually be that bad by 2100. Although I won’t be here, I don’t want my children’s children’s children to be affected by our bad choices made in 2009.

  47. Cynthia McPherson says:

    If enough people become aware of the issues, they will demand that governments take appropriate actions. Therefore, it is essential that people become informed. Local GW groups might help. World wide marches and uprisings come to mind…

    Also, I’m tacking a poster at the Health food stores in our area in which I’m pledging to refrain from using my car 2 days out of the week and ask others to also commit. If the administration and Congress won’t commit then we the people can. “2 days off fossil fuels, 4-5 days on.”

  48. Cynthia McPherson says:

    For those who don’t believe we humans are capable of having an affect on the climate… Think! Carbon dioxide is a green house gas. There are about 5 billion people on the planet. Around the middle of this century, there will be about 9 billion. It’s true that in the old days, horse and buggy days or whatever, we weren’t affecting the environment that much. Things are different now. Population explosions and all those humans driving cars, using AC and Heating their homes. Lots of fossil fuels useage nowdays. Doesn’t take a genius to figure it out! Fossil fuels have allowed us humans to proliferate like never before. The planet is being overrun with the human species… the planet has a way of correcting things. The planet will survive. The question is, will we??!!

  49. Glenn Fay says:

    It would be wise to push out the systemic impacts farther than you have to show how rising sea levels and the loss of fresh water will create displacement of at least several billion people and very likely lead to world wars over survival resources.

  50. Cynthia says:

    According to the book, “Boiling Point”, one group of IPCC scientists, who focused their research on the outcome of global warming, “…came to the extremely sobering conclusion that most of the Earth’s inhabitants would be losers.”

  51. Cynthia says:

    Just read last night (I believe from ecoSanity but not sure!) that about 1 billion people will be left when all this is over, by the end of the century. (One billion out of nine billion– not good odds!)

  52. Cynthia says:

    Impacts by 2100? …possibly the shifting of the poles. With large scale crustal displacement/ice the Earth’s axis will shift (“so that where there have been those of a frigid or semi-tropical will become the more tropical, and moss and fern will grow”), but this may come later.

    The Thermohyline Cycle (Ocean Conveyor belt)may become disrupted.

  53. Cynthia says:

    … then there are the social implications, which you didn’t ask for. (A profound sense of discontinuity, resulting in sharp increase in violence, social upheavals, etc.) But I won’t go there, as much as I would like!

    Let me just include this one thing: An interview with Brazilian natives revealed extreme stress as the natural phenomena they’re used to depending on for survival, for growing crops, etc, was disappearing. And this is just the very beginning!

  54. Sameer says:


    Can you please explain why people seem to be saying that we only have a small window to address climate change, like in the next 5 to 10 years? If we don’t act in that time frame, will there be some type of a rapid acceleration that will cause us to reach the tipping points very soon thereafter?

  55. john says:

    thanks for the great info on global warming

  56. Cynthia says:

    Do you see the posts as we are writing them, because you respond awfully fast!

    [JR: I see them right after they are posted!]

  57. dvcyril says:

    information given is sufficient to awake the readers.popularising the necessity of immediate action is the need of the hour.we all shall do that for a living planet.

  58. Great summary… but couldyou please use metric numbers as well as US ones? Inches and fahrenheit don’t resonate with most international readers (except some older British ones).

  59. VASU MITTAL says: