What Are The Measured Impacts Of Anthropogenic Climate Change To Date?

I really want to know the answer or answers to that question. I’d really like to see a list that scientists from both sides can agree on.

My impression from reading about global warming every day since 2008 is that there are few if any measurable impacts so far–with two notable exceptions.

Human contributions to global warming are generally thought to have commenced on an industrial scale during or shortly after World War II. However, temperatures chose just that time frame to have a 30-year lull that resembles nothing so much as the recent ‘stall’ in temperatures since 1998, noted by skeptics everywhere and James Hansen, if nobody else on the activist side.

Temperatures then rose rapidly between 1975 or so and 1998 or so, amounting to about 0.5C. What has that done to our planet?

The one thing most everyone agrees on is that the Arctic has been affected–temperature rises there were not 0.5C but closer to 2C. There isn’t as much ice as before 1975 and it melts more extensively in the summer. The IPCC also estimates that the duration of ice cover over rivers and lakes has decreased by two weeks over the course of the 20th Century in the mid and high latitudes of the Northern Hemisphere. They also note a lengthening of the growing season by four days on average.

But what else? There are hundreds–no, thousands of articles and papers on the subject but most are describing a possible future, not the present.

An ornithologist named Keith Butler of Oxford’s Department of Zoology catalogued some of the observed impacts in a paper published in 2003.

Butler writes, “Over the past century, the Earth has warmed by approximately 0.5 °C (von Storch & Navarra 1995, IPCC 1998). During the past 10 years, a variety of studies have shown that global climate change is affecting the world’s flora and fauna. The active growing season of plants has advanced by 8 days in northern latitudes (Myneni et al. 1997).”

There are other changes in species behavior. Butler continues, “Studies on birds have shown that diverse avian taxa are now nesting significantly earlier in both the United States and Europe (Kruk et al. 1996, Crick et al. 1997, Forchhammer et al. 1998, McCleery & Perrins 1998, Visser et al. 1998, Brown et al. 1999, Crick & Sparks 1999, Dunn & Winkler 1999). Surprisingly, however, a widespread change towards an earlier arrival date in migrant birds, although demonstrated on the European continent (e.g. Sokolov et al. 1998, Sparks et al. 1999, Sparks & Mason 2001, Tryjanowski et al. 2002), has not been demonstrated on the North American continent. Although a few studies have shown that individual species are altering the timing of their migration (Bildstein 1998, Inouye et al. 2000, Pulido et al. 2001), studies examining the arrival or departure dates of multiple species have shown that whereas some species are arriving significantly earlier, others are arriving significantly later (Mason 1995, Oglesby & Smith 1995, Bradley et al. 1999, Wilson et al. 2000, Zalakevicius & Zalakeviciute 2001).”

In the Discussion section of his paper Butler says that 28 of 103 species migrated earlier, and no species migrated later. But he didn’t write on whether this was good or bad for the species or those species with which they interacted.

The IPCC technical paper linked to above states categorically that ranges for plants and animals have shifted polewards and upwards. That plants flower and insects emerge earlier.

But has global warming had a positive or negative effect to date? Do we have an idea of how climate change has affected biodiversity?

The IPCC’s Technical Document describes studies of hundreds of species. They note a variety of changes. Again, most are simply that–changes. The IPCC doesn’t say whether the changes harm, have no effect or even help the species affected.

But in some cases they describe real problems. It probably comes as no surprise that some species of plants and animals are experiencing severe difficulties.

Reading the IPCC’s document it struck me that in almost every case of a species in trouble, they made it clear that climate change was a contributing factor, not the only one. And in no case did they specify climate change as the principal problem. Throughout you see sentences like,

  • “…shorter term variations in North Sea cod have been related to a combination of overfishing and warming over the past 10 years.”
  • …”(Coral) bleaching effects are also associated with pollution and disease…”
  • …”Along the Aleutian Islands, the fish population driven by climatic events and overfishing has changed, thus changing the behavior and population size of killer whales and sea otters…”

As I’ve noted before, climate change may be expected to serve as the unwelcome straw that broke the camel’s back for some unlucky species–but the principal threats mankind poses to biodiversity are and will remain for some time to come, habitat loss, hunting, introduction of alien species and pollution. (The four horseman best described by Matt Ridley, who’s still busy disagreeing with me over on another thread. Sigh.)

Of course the iconic example of the threat to biodiversity is the polar bear. However, anyone who has been following their trials and travails will have read that their population is increasing, not decreasing, mostly due to the halt on hunting put in some decades back.

So I would submit that global warming so far has not been more than an annoyance for the biome of this planet, especially in comparison with the rest of man’s follies.

What about sea level rise? It has been rising at between 1 and 3 millimeters per year for quite some time now. Has it had an effect so far?

From Wikipedia

From Wikipedia

Sea level appears to have risen about 8 inches since 1880. Have people moved? Have storm surges been more damaging? We saw with Sandy that timing is important–the storm hit at high tide and that didn’t help. But was it made even worse by the sea level rise due to global warming?

Scott Mandia certainly thinks so. He told Chris Mooney in an article for Mother Jones “I keep telling people the one lock you have here is sea level rise,” meteorologist Scott Mandia explained to me recently. “It’s the one thing that absolutely made the storm worse that you can’t wiggle out of.” That’s… an interesting choice of words. He must have expected a challenge. He won’t get one here.

…”First, according to sea level expert Ben Strauss of Climate Central, the sea level in the New York harbor today is 15 inches higher than it was in 1880. Now, to be sure, not all of that is due global warming—land has also been subsiding. Strauss estimates that climate change—which causes sea level rise both through the melting of land-based ice, and through thermal expansion of warm ocean water—is responsible for just over half, or eight inches, of the total.”

…”But as it turns out, eight inches matters a lot. First of all, using Climate Central’s Surging Seas tool, Mandia estimated that 6,000 more people were impacted for each additional inch of sea level rise. That means, basically, that they got wet when they wouldn’t have otherwise: one inch wetter for some, eight inches wetter for others, and everything in between.”

So an extra 50,000 people may have been affected by Sandy because of global warming. And that sounds about right to me. It would be impossible to guess how badly they were affected out of the millions of victims of the storm. But 50,000 is enough to make a difference.

I need to tie this up for the evening–may return to it later. I wanted in this piece to put a line in the sand saying this is what global warming has done to date. Looking at some of the high profile impacts that have been signaled as future problems, I think we can say the following:

  • The Arctic has been heavily impacted by global warming. Temperatures have risen about 2C, ice is thinner and less extensive and melts more dramatically each summer.
  • We have noted real changes due to warming in the timing of seasons and the response of plants and animals to it. We haven’t see much in the way of evidence that either plants or animals have been harmed so far.
  • Global warming so far amounts to an additional stressor to species already endangered by our other actions–hunting, introducing alien species, habitat loss and pollution, the sum total of which far outweighs the negative effects of climate change to date.
  • Sea level rise seems to have contributed to the destructive power of storms, increasing the areas affected. This is a real effect and should not be discounted or ignored.

I’d welcome additional comments on this. I spent two hours on this post and I know it is not enough for a subject of this magnitude. But it’s what I have to offer on a Monday evening.

34 responses to “What Are The Measured Impacts Of Anthropogenic Climate Change To Date?

  1. Hi Tom, ” The one thing most everyone agrees on is that the Arctic has been affected–temperature rises there were not 0.5C but closer to 2C.”

    Just curious – are you suggesting this is anthropogenic? I then scrolled back to see the title of the post ( What Are The Measured Impacts Of Anthropogenic Climate Change To Date?). Who knew?

    • Hiya Bob–I think a goodly part of it is. CO2 plus black soot plus deforestation plus who all knows what else.

      • Tom, you just might be guilty here of what you recently accused Ridley of, i.e. a hasty effort not up to your own standards. You make a definitive in the post above without evidence. Better to refer to it as speculation, don’t ya think.

  2. Tom, ” Sea level rise seems to have contributed to the destructive power of storms, increasing the areas affected. This is a real effect and should not be discounted or ignored.”

    I am looking hard, yet in vain, to see how you draw this scientific conclusion. I trust it didn’t come from Mandia. I recall Mandia, in his sophomoric attempt to have a stats discussion with VS, admit the only course he ever took in stats was an Introduction of Statistics for Science Majors course.

    • Well, he used someone else’s calculator 🙂

      It’s not a scientific conclusion, Bob. I’m not a scientist. I can follow the math but am not competent to decide on the input values to the equations.

  3. Tom, ” So an extra 50,000 people may have been affected by Sandy because of global warming. And that sounds about right to me.”

    Now Tom, let me see if I can connect the dots. We are currently in a hurricane drought ( http://rogerpielkejr.blogspot.com/2012/12/record-us-intense-hurricane-drought.html), global temperatures are flat for the past 16 years, and real sea level rise is decelerating. Makes sense now.

    • Glad it makes sense to you–it doesn’t to me. Hurricane landfalls don’t really mean much. It’s formation, power and extent that count, no matter which direction they move in.

      • Tom, but where did the “power” come from? Even Dear Leader would not attribute Sandy to AGW, at least not definitively.

  4. ” Temperatures then rose rapidly between 1975 or so and 1998 or so, amounting to about 0.5C. What has that done to our planet?”

    As far as I can tell, nada, zilch, niente, niets, bupkis, גאָרנישט

  5. Tom are you making the standard mistake of failing to add benefits before subtracting negatives?

    Your list looks pretty weak. And trivial when compared to other environmental impacts such as habitat loss due to human population expansion, etc.

  6. Hi Tom,

    Interesting post. I’ve been thinking about this for a while myself. We can see impacts in a few areas that are directly related to temperature.

    I’m not buying the sea-level flood risk though. I find the 50K people idea as amusing as it is bizarre. First, the number of people affected depends on where people reside – low or high. Second, it’s a trivial problem. There’s no need to speculate. There’s probably excellent elevation data for NYC and surrounding areas (<1m?). And there's definately excellent GIS data on population and land use. Stack the two and fill the bathtub. Third, the USACE has probably already done the work.

    So I'm not sure how our expert arrived at his numbers but, unless he used the method described above I wouldn't put much stock in it. But I could play along for argument's sake.

    So we have 15 inches of – let's be technically correct here – I think you mean relative sea level rise in the NYC area? If we attribute 8 in to AGW, what do we attribute the other 7 in to?

    One possibility is that the lowland area that NYC is built upon is subsiding due to lack of sediment replenishment. Flood plains sink over time as the sediment compacts. Normally, rivers continually build up their flood plain by dumping sediment on it when they flood. I suspect it’s been some years since NYC has seen a flood on the Hudson.

    If that’s the case, then development and AGW are making roughly equal contributions to exposing people to additional flood or surge risk. So what’s the argument for mitigating one without mitigating the other?

  7. Looking at the long term sea level rise, rate of rise from 1920-1950 is about the same as 1950-2010. IPCC AR4 argues that anthropogenic CO2 levels were too low prior to 1950 to have a detectable impact on climate. Therefore, once you subtract natural sea level rise, you have nothing left over to attribute to anthropogenic causes. (That is measurable anyway.) The situation may be different in the future, but right now the impact is about zero or close enough to zero for us not to need to consider it.

  8. Tom,
    You asked a question few if any ‘pros’ have dwelt on. The inconvenient truth is that AGW is more like waiting for Godot than a great crisis.

  9. Tom,
    Sorry for the two posts, but I am getting a busy day started.
    It is sad that you have held out SLR as
    1- a significant issue
    2- attributed it to CO2
    3- asserted that it is causing damage from storms to increase
    Not to put too fine a point on it, but slr, like OA, is utter bs, a fabricated crisis linked to a fantasy cause.

  10. NYC should have been prepared for what they saw last year. Sea levels are only up about 3 inches in the past 30 years. To a certain extent Bloomberg is using AGW as a scapegoat to deflect criticism from his own city’s lack of preparedness.

    What almost everyone agrees on is that infrastructure should be protected. Every state/city/county must make it’s own risk trade-offs by looking into their own crystal balls and assessing costs. It is perfectly OK to include an “acceptable losses” category in this assessment. Nobody talks about this, but this is what is done. You don’t spend $50M protecting a $5M asset.

    NYC got unlucky. The perfect storm hit at high tide, but surely they knew this was a possibility.

    What I think everyone also agrees on is that implementing a carbon tax or global treaty or stopping Keystone is not going to stop another Sandy from happening. They need to protect infrastructure regardless of the action on climate.

    If they don’t they will bear the consequences, and the blame should be on them, not a SUV’s tailpipe.

  11. Another nice post, and I hope you get an answer to your question. Personally, I’ve no doubt that changing climate will effect the weather. I’ve also tried moderately hard to find an answer to one of the other questions that bothers me: “Are there theoretical reasons why climate would not without forcing drift a degree or two over 100s and 1000s of years?” Nothing much so far, p’raps you can help?

  12. Pingback: The Next 60 Years of Lukewarming | The Lukewarmer's Way

  13. There are FAR too many measured impacts to ever list them all here.

    Changes in atmospheric water vapor content, albedo shifts, alterations in local gravity and pressure as solid ice becomes liquid water and is relocated, growth of the Hadley cells, weakening of the Arctic gyre, greater wave amplitude in the jet stream and other mid latitude wind patterns, countless impacts on individual plant and animal species, coral bleaching, et cetera.

    Even the IPCC reports only touch on the major impacts and general themes. A complete record would take decades to compile and then be completely out of date.

    • You’re talking about changes. Changes are not impacts.

      • I do so detest semantic nonsense.

        How is the sea level rise YOU list an “impact”, but NOT a “change”? Sea level rose without changing?

        All of the things I listed are “impacts” of AGW. Planetary albedo did not shift on its own. It did so because the planet got warmer. Yes, that is a “change”. It is also an “impact”.

      • Umm, you’re not making too much sense here, CBD. At least not to me. Want to try again?

      • “Umm, you’re not making too much sense here, CBD. At least not to me. Want to try again?”

        Yes, well it CAN be difficult to understand a reply when the message it is responding to has been deleted.

        Though… given that you WROTE the missing message in question I’d think you’d be able to puzzle it out. Oh well… as your objection to my first comment has disappeared we are apparently in agreement. :]

      • Urkk–I didn’t delete any of your comments, CBD. Let me check what’s going on.

      • Okay–I restored one of my comments that ended up in the trash–I’m censoring myself, oh noes!

        I don’t agree with you. And your previous comment did not make sense to me. The way I am trying to express myself is that the climate changes. Some of the changes are caused by humans. Some of the changes have impacts. Now, I’m not asking you to agree with me, but does my approach at least make sense to you?

      • Tom,
        Discussing something like climate with an extremist like CBD is truly a pearls before swine effort.

  14. 1. I think that a game changing paper on seal level rise will come out in about 2 weeks. I’ll review it then.
    2. I think that the arctic ice melt is man made, but mostly black carbon and changes in circulation due to land cover change and waste heat. Someday I’ll try to explain the mechanism better.
    3. If you’re worried about biodiversity (I am) and threats to near shore dwellings (I’m not) , kill two birds with one stone. Make the shoreline a wildlife preserve.

  15. Conrad Dunkerson

    “The way I am trying to express myself is that the climate changes. Some of the changes are caused by humans. Some of the changes have impacts.”

    What is the criteria you are using to decide which changes do and do not have impacts? Because that is some sort of purely semantic distinction at odds with normal usage of the terms. How does your example of sea level rise meet your definition of “The Measured Impacts Of Anthropogenic Climate Change” in a way that my example of albedo shift does not?

    • All climate change has impacts.
      All change has impacts.
      The question is are they significant, are they positive, or are they negative.
      So far climate change impacts have been insignificant at most.

  16. People build by the shoreline then complain about flooding from storm surges. People build under airport flight paths then complain about the noise. People build in California then complain about drought. F’heavensake people build next to farms then complain that they don’t want their children to see animals having sex. The cause has nothing to do with global warming (a fact which I do not dispute). It has everything to do with human cupidity and human stupidity.

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