Increases in rainfall extremes linked to global warming (reprint)

2011-queensland-floods-the-big-wet

The flooding in Queensland and New South Wales was a devastating and record breaking. Despite claims that increased rainfall somehow disproves the reality of climate change, such extremes are to be expected in a warming world. Seth Westra of the University of Adelaide has a good article on the topic which I’ve republished below. Note, it originally appeared on The Conversation. – Mike @ WtD

Increases in rainfall extremes linked to global warming

Seth Westra, University of Adelaide

Rainfall extremes are increasing around the world, and the increase is linked to the warming of the atmosphere which has taken place since pre-industrial times. This is the conclusion of a recent study which investigated extreme rainfall trends using data from 8326 weather-recording stations globally, some of which have records spanning more than a hundred years.

Of all the stations analysed, we found that two-thirds showed increasing trends over the course of the 20th and early 21st centuries. When we looked at the association between the intensity of rainfall extremes and a record of global mean near-surface atmospheric temperature, rainfall intensity was found to increase at a rate of between 5.9% and 7.7% for each degree, depending on the method of analysis.

This kind of change is precisely what can be expected if one assumes that the intensity of the most extreme rainfall events will scale with the capacity of the atmosphere to hold moisture. This is well known to increase with temperature at a rate of about 7% per degree.

Looking beyond globally averaged numbers, however, we also found distinct regional differences. The greatest increases occurred in the tropical belt; the smallest in the drier mid-latitudes where you will find most of the world’s deserts. In the higher latitudes, particularly in the northern hemisphere, the rate of change was close to the global average. Again, such changes seemed to be in quite close agreement with what global climate models say should happen as a result of global warming: a reassuring case of observations confirming theory.

The implications of this are likely to be significant for flood risk around the world. It’s true that 7% per degree doesn’t sound like much. But if we continue to follow the current trajectory of greenhouse gas emissions, we can probably expect in the order of three to five degrees of warming by the end of the 21st century. If the relationship between extreme rainfall and atmospheric temperature continues to hold, then this could mean as much as a 35% increase in extreme rainfall intensity on average globally.

What does this mean for the capacity of our infrastructure to handle current and future floods? Most flood-defence infrastructure, such as dams, levees, stormwater systems and coastal flood defences, has been designed to handle historical flood risk. If the risk of flooding increases, then such infrastructure will have increasing difficulty managing floods in the future. This would either lead to increased damage costs due to the flooding, or necessitate expensive infrastructure upgrades or resettlement of low-lying communities. Even the increase in extreme rainfall intensity observed thus far is likely to lead to substantial challenges for some existing infrastructure.

Nevertheless our analysis should not be interpreted as suggesting that the rapid increase in flood damage which has occurred over the past few decades is entirely attributable to climate change.

In fact, other changes such as deforestation, rapid urbanisation and an increase in the number of people living in flood plains are likely to account for the bulk of these changes. Furthermore, not all floods are caused by extreme rainfall events. Snow melt and storm surge also contribute to overall flood risk. Antecedent moisture – the wetness of the catchment prior to the flood-producing rainfall event – can also have a substantial influence on flood risk. In some parts of Australia this might even cause flood risk to decrease because of an expected increase in the number or severity of future droughts.

Despite all these caveats, our recent study contributes to the debate on how climate change will affect flood risk, by showing that the intensification of rainfall extremes is not just a projection made by climate models. Rather, it can already can be detected in our observational record.

Seth Westra receives funding from the Australian Research Council, CSIRO, Engineers Australia, Geoscience Australia and AusAid.

The Conversation

This article was originally published at The Conversation.
Read the original article.

50 thoughts on “Increases in rainfall extremes linked to global warming (reprint)

  1. shirl says:

    Which part of 4.5 Billion years of climate change don’t you understand.Climate Change is NATURAL and without CO2 there would be no Life on Earth get over your Doom and Gloom pull your head out of your arse open a window and enjoy our beautiful EVER CHANGING World,Cheers mate have a great day.

    • john byatt says:

      Please post your evidence from scientific papers that the current global warming is natural and not due to increased greenhouse gas due to humans.

      will not hold my breath waiting

    • zoot says:

      For most of those 4.5 billion years there were no humans (or other animals and plants) on the planet.

    • Bernard J. says:

      Shirl.

      Every time that climate changed ‘naturally’ in the fashion that it is currently occurring, there were great extinctions.

      And the current rate of release of CO2 into the atmosphere is greater than the rates that occurred during those great extinctions.

      You might like the idea of heating the planet to another Great Extinction, but there are rather a lot of us who would beg to differ.

  2. Eric Worrall says:

    Interestingly this post is on the same page as today’s Willis Eschenbach post on WUWT – he also predicts global warming is likely to slightly increase storm activity.

    http://wattsupwiththat.com/2013/02/07/emergent-climate-phenomena/

    The difference is you aren’t taking account of the cooling effect of storms. Storms are massive heat pumps, they transport heat carrying water vapour to the top of the atmosphere, where it dumps its heat directly into space, unimpeded by the greenhouse blanket. Storms can only occur when the water vapour they contain cools enough to form clouds – so the water vapour keeps rising up until it reaches a cool enough region to dump its heat.

    Of course the heat pump effect is not the only way storms cool the surface. High albedo storm clouds also reflect sunlight back into space, preventing a lot of the heat from ever reaching the surface.

    Since storms reduce surface warming, they represent a massive negative feedback against CO2 forcing.

    Now all we need to do is figure out how to pump the extra rain to regions which could really use it, and everyone is happy.

    • Watching the Deniers says:

      I’ll actually go read that Eric. So Willis is accepting some warming?

      • john byatt says:

        They belive that moving energy around the planet equates to removing it from the planet,

      • john byatt says:

        For every degree of temperature increase the hydrological cycle increases by about 2%, that ain’t gonna save us

        This is not to be confused with the 7% increase in precipitation

      • Watching the Deniers says:

        Thanks John, I’m just picking my way through it. You’re comments are spot on from what I see.

      • Eric Worrall says:

        Every movement has its cranks, but mainstream skeptics accept there will be some warming. The main difference between our positions is whether the warming will be beneficial or catastrophic, and whether the cost of reducing emissions is justified by the benefits (if any).

        There are encouraging signs of a convergence. Some members of the alarmist community are toying with the possibility that climate sensitivity is lower than they previously feared.

        http://wattsupwiththat.com/2013/02/01/encouraging-admission-of-lower-climate-sensitivity-by-a-hockey-team-scientist/

        It doesn’t take much of a reduction in climate sensitivity to make the alarming consequences go away. Given that the rate of technological progress is accelerating, IMO it is extremely unlikely we shall still be using the same energy mix in 50 years – so it doesn’t take much of a reduction in climate sensitivity to remove the need for alarm and expensive countermeasures.

      • Watching the Deniers says:

        It’s a variation of Lindzen’s arguments about the cooling effect of clouds and the climate system “regulating itself” to negate the warming trend and save the day (i.e. wishful thinking). A long post, but essentially the point is made in these quotes:

        “The emergence of clouds and thunderstorms radically cooling the surface, plus the increase in convection and evaporation with temperature, plus the thermal radiation going up as the fourth power of the temperature, all combine to put a serious barrier in the way of any increases in temperature.”

        And:

        “So when the forcing from CO2 increases a watt or two, in an accurate model the clouds will emerge a few minutes earlier on average across the tropics, and the balance will be restored. This system of control by emergent phenomena has worked very well for billions of years, and it handles large swings in radiation every single day—it won’t be altered by a few watts of extra forcing from CO2.”

        See NYTimes article here – this theory has long been debunked;

        http://www.nytimes.com/2012/05/01/science/earth/clouds-effect-on-climate-change-is-last-bastion-for-dissenters.html?pagewanted=all&_r=0

        “…in recent years, the climate change skeptics have seized on one last argument that cannot be so readily dismissed. Their theory is that clouds will save us.

        They acknowledge that the human release of greenhouse gases will cause the planet to warm. But they assert that clouds — which can either warm or cool the earth, depending on the type and location — will shift in such a way as to counter much of the expected temperature rise and preserve the equable climate on which civilization depends.

        Their theory exploits the greatest remaining mystery in climate science, the difficulty that researchers have had in predicting how clouds will change. The scientific majority believes that clouds will most likely have a neutral effect or will even amplify the warming, perhaps strongly, but the lack of unambiguous proof has left room for dissent.”

      • john byatt says:

        God of the gaps.

      • Eric Worrall says:

        You’re making an assumption that this “gap” is unimportant John.

        The empirical reality is that the world hasn’t warmed for 16 years, despite an enormous load of CO2 dumped into the atmosphere. Current generation climate models have been caught with their pants down – hence the MET’s “experiment” with new models which predict lower warming, at least for the next 4 years.

        http://www.bbc.co.uk/news/science-environment-20947224

        If CO2 emissions lead to slightly increased rainfall, rather than substantially increased temperatures, then a lot of alarmist predictions are hopelessly wrong.

        Closer to home, if Willis is right, Australia has just wasted billions on desal plants which will be unnecessary in a warmer, wetter world – the billions would better have been spent on flood control measures. An object lesson in how much waste of precious public resources can occur when people respond to unconfirmed theories rather than empirical measurements.

      • zoot says:

        The empirical reality is that the world hasn’t warmed has continued to warm for the last 16 years …

        FIFY

      • Dr No says:

        Sceptics of water desalination plants should take a trip across the Nullabor and ask the residents of Perth what they think about them.

        They should also ask Brisbane resident about the value of desalination during the floods. (Eric recently got egg all over face for slagging them just before finding out they were operating at 100% capacity in order to provide non-polluted water)

        They should also ask themselves what will happen if the current dry spell is a return to the pattern seen before the last La Nina event.

    • zoot says:

      tag fail, sorry

    • Eric, in reply to one of your later comments, I would like to agree with you on one of your points. Yes, in my opinion, some states of Australia have wasted Billions on desalination plants.
      The same water security could have been obtained through changes in government policy that would actually save money, be good for the environment generally, and reduce Australia’s output of Carbon dioxide.
      However, a general increase in rainfall in Australia does not mean an increased level of water security for all parts of the continent.

      • john byatt says:

        Which states do you belive have wated money on desalination plants Steve ?, I am not comming from the position of in hindsight either.

        It is worthy of discussion

      • When I wrote that comment, I was specifically thinking of South Australia where I live. In SA there was a prediction made of our future population growth, suggesting that our population would shrink significantly. The state government did not like this and has pursued an aggressive, but not entirely successful, policy of deliberately increasing our population.
        Of course the commonwealth government also has a similar policy nationally, and in 2004 the federal government introduced a number of things to raise the birth rate of the country. These measures are mostly still in place although the government changed parties a few years ago.
        There was a drought, and for the first time that I remember the South Australian government put restrictions on residential water use. There have been other droughts in the past, but an increased population generally means more water is used. The drought was caused by lack of rain, almost certainly contributed to by climate change (A lower winter rainfall in our state is one of the predictions made, and this definitely appears to be happening) but the water shortage was caused by government policies.
        The state Liberal party suggested a desalination plant and the labor government eventually built it, although the Liberal Party did not support the way they did it. Of course the Greens opposed it.
        In my view, the prime reason for possible water shortages in the future in South Australia (Supposedly the driest state in the driest populated continent) is the planned deliberate increase in population, not climate change.
        I know much less about the desalination plants in other states, but I suspect that the need for them in Victoria could also have been avoided with different policies.

      • john byatt says:

        Victoria’s plant has a 100 year life from what I have read and the water levels are again falling with a long term projection of low rainfall,

        I thought that the SA plant being run by renewable was what they all should have done,

        It will allow future environmental flows in the murray ?

        I see them as security, queensland has had to bring the tugun plant online twice during the floods, it may still be supplying but it is not mentioned,

        The attacks on the plants are purely in hindsight. perth could not survive without their plant. i think that Mike is planning a post sometime in the future,

        one thing i do know is that they were not built because of what tim flannery may or may not have said .

        will research before mikes post re same

      • zoot says:

        Without desal in (south west) WA we’d be depleting our groundwater at a completely unsustainable rate.
        An unintended (I think) byproduct of bringing the desal plants on line is an improvement in the quality of Perth’s drinking water.

      • John, the criticisms of the SA desalination plant were started well before it was built so they were not all attacks in hindsight.
        You are correct in saying that one of augments put in favour of the plant was to allow environmental flows for the Murray, but this was before it was built. After it was built, the state government announced that it would not reduce the amount of water taken from the Murray.
        The government also certainly talked about using renewable energy for running the plant. The power for it is taken from the general grid that uses a mixture of renewable and fossil fuel (including brown coal) electricity. There is a serious proposal to replace the aging brown coal power plant at Port Augusta with a (larger) solar thermal one with liquid salt storage, but so far it is just a proposal.
        I accept the need to for the desalination plants in Western Australia, and at least one of these (on Rottnest Island) is being run on wind power.
        However, there is a serious danger of very rapid changes in the climate is being used generally as an excuse for things mainly caused by government policies. The deliberate increase in the population of the country will increase the need for desalination plants and other energy hungry technologies.
        I will definitely look forward to any post on these subjects by Mike, (and to comments by you).

  3. john byatt says:

    Karen has two good guest posts at RC on climate sensitivity part one and two.

    comments

    Karen Shell says:
    4 Jan 2013 at 10:19 AM
    The feedbacks in these posts are defined from the top-of-the-atmosphere (TOA) perspective. A positive feedback increases the net absorption of radiation by the planet when the global average temperature increases (i.e., the increase in absorbed solar radiation is greater than the increase in outgoing longwave emission). In the case of water vapor, for example, the outgoing longwave radiation (W/m^2) _de_creases with temperature (K), so it’s a positive feedback.

    Evaporation and precipitation don’t directly affect the TOA energy budget. They merely redistribute energy within a column (and horizontally if the evaporation and precipitation occur in different locations). Of course, this could alter the temperature, water vapor, surface albedo, and cloud structure. Thus, the TOA effects of changes in evaporation and precipitation are indirectly included in the other feedback terms.

    Evap and precip are extremely important for the surface energy budget, but that a whole other post.

  4. john byatt says:

    Could have guessed that WTFIUWTt would not understand Annan

    but what would the difference be between a cs of 3 and one of 2.5

    about one decade extra to prevent temp exceeding 2DegC

    Annan confirms that the likely CS is likely 3, and his 2.5 is clearly within the IPCC range of 2 to 4.5,

    Of course none of the deniers has bothered to read his paper nor his blog

  5. john byatt says:

    Something quite funny just hit me. black humour

    the claim that there is a missing hot spot,

    well if their is we can kiss the negative feedback from that goodbye and expect that models are underestimating the likely warming

  6. john byatt says:

    A 69 foot rise in sea level is not as bad as we thought

    here is the chart.

    http://tamino.files.wordpress.com/2013/02/sealevel.jpg?w=500&h=499

  7. john byatt says:

    Remember that Goddard got the boot from WUWT for his persistent stupidity,

    surely after Willis Eschenbach’s recent idiotic posts he will shortly follow the same fate?

    willard does not wish to become any more of a laughing stock does he?,

    maybe they could get worral to do a eugenics post as they go down the credibility gurgler .
    .

    • john byatt says:

      Then again maybe not

      QLD tick warning update

      After floods, conditions favour the survival of ticks and a rise in tick burdens should be expected. With this rise in ticks, there may also be an increased risk of tick fever, especially if tick numbers have previously been low. With low tick burdens, animals may have reduced immunity to tick fever. It is recommended that you increase monitoring for ticks and tick fever, and take preventative actions where possible.

  8. john byatt says:

    Newman “praise the lord that the floods missed the coal”

    http://www.abc.net.au/news/2013-02-08/newman-says-post-flood-economy-will-bounce/4508704

  9. eworrall1 says:

    Mike, you’re being far too timid about announcing your accomplishments – you should have told us how involved you are with the Lewandowsky effort.

    http://joannenova.com.au/2013/02/lewandowsky-dismisses-bloggers-but-they-are-his-research-team-who-is-mike-hubble-marriott/

  10. john byatt says:

    Aha this site is all a trick to get deniers here and track them down

    at novacaine

    Mark D.
    February 8, 2013 at 5:59 am · Reply
    I refuse to go there because of the probability that someone will be tracking the traffic, collecting the IP addresses and then “studying” them.

    ,

    • john byatt says:

      Mike did post that he was involved with the paper, some of these retards cannot read a blog post let alone a science paper

  11. john byatt says:

    .

    research firm Bloomberg New Energy Finance has concluded that electricity from unsubsidised renewable energy is already cheaper than electricity from new-build coal and gas-fired power stations in Australia.
    The modeling from the BNEF team in Sydney found that new wind farms could supply electricity at a cost of $80/MWh — compared with $143/MWh for new build coal and $116/MWh for new-build gas-fired generation. These figures include the cost of carbon emissions, but BNEF said even without a carbon price wind energy remained 14% cheaper than new coal and 18% cheaper than new gas.
    “The perception that fossil fuels are cheap and renewables are expensive is now out of date,” said Michael Liebreich, chief executive of Bloomberg New Energy Finance. “The fact that wind power is now cheaper than coal and gas in a country with some of the world’s best fossil fuel resources shows that clean energy is a game changer which promises to turn the economics of power systems on its head,” he said

    • Skeptikal says:

      I fully support your argument for the removal of all subsidies for renewable energy. The subsidies are clearly no longer warranted and should be removed immediately. I’ll hunt down that article and send a copy to Tony Abbott.😉

      • While you’re at it, could you ask him to please start taxing aviation fuel? Oh, oh yeah, and ask him why fossil fuel is subsidised by being allowed to pollute for free. How you’re going to do that using only monosyllables so that he understands may prove difficult, admittedly, but give it a try.

      • Skeptikal says:

        You communist-greens want to tax everything.

        Go ask him yourself.

      • Gosh, Skeptikal, I thought you were against subsidies. No?

        It’s fair your petrol is taxed but elitists (like me) can fly on tax free aviation fuel? Really? How about taxing aviation fuel and reducing sales tax – make it fiscally neutral? Tony would love it, surely,

        You don’t like small renewable subsidies but you’re ok with large fossil subsidies. Care to explain that anomaly? http://environment.nationalgeographic.com/environment/energy/great-energy-challenge/global-energy-subsidies-map/

        I’m not all that surprised to see you shying away from the who pays for pollution discussion. It’s easier for the factually challenged to simply close their eyes, mumble “lah, lah, lah, Climategate, hide the decline, Al Gore, Amen”.

  12. john byatt says:

    Nova the gift that keeps on giving

    I had replied to a denier letter in the local paper, he cited Nova, i replied that she was a conspiracy theorist,
    they passed my letter on to her as they printed a letter from her a while later
    It went on for a few paragraphs how she was not a conspiracy theorist and finish off with “climate change is all about power and money”

    The reason that i do not comment there is because of Spatch’s experience, being bombarded with her propaganda via email.

    He told her to Fuck off and was banned,

  13. john byatt says:

    Read the title of the above post and then contemplate this gem

    Skeptikal
    February 8, 2013 at 4:48 am · Reply
    Who knows what other crackpot things he has to say on his site?

    I go there occasionally, but I’ve yet to see any real science content.

    I find he mostly posts about weather events… calling every weather event “the new normal”. He must really believe that Australia never had bushfires or floods or storms before the advent of the AGW theory.

    Apart from that, he blogs about newspapers or other blogsites which publish things he doesn’t like to hear about. He complains about cherry-picked data and people giving out mis-information and things like that.

    The name of his site is a bit off-putting to skeptics, but maybe that’s intentional. He does allow dissenting comments, but the name of his site probably limits the number of skeptics who would go there in the first place.

    Skeptical obviously does not go beyond the post title

    • Skeptikal says:

      I don’t see what the post title has to do with it. I was responding to another commenter who said…

      Who knows what other crackpot things he has to say on his site?

      If you can’t understand the concept of commenting on someone else’s comment, then you really shouldn’t be using the internet unsupervised.

      • john byatt says:

        just how dumb are you? my comment was about your reply to that first line

        would someone who comes to the site ask … “what other? etc

        good grief

  14. john byatt says:

    another gem

    JunkPsychology
    February 8, 2013 at 1:22 pm · Reply
    In the United States, where many believe they have a religious obligation to reject evolution, those who question doctrines of catastrophic anthropogenic global warming are commonly accused of being creationists.

    I didn’t realize that the same method of guilt-by-association was being employed in Australia.

    you said guilt by association JP not me

    bet the creationists there are a bit red faced

  15. […] 2013/02/07: WtD: Increases in rainfall extremes linked to global warming (reprint) […]

  16. Bernard J. says:

    Does anyone know the back-story to the image at the top of the thread?

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