Odds that global warming is due to natural factors: Slim to none

Statistical analysis rules out natural-warming hypothesis with more than 99 percent certainty

An analysis of temperature data since 1500 all but rules out the possibility that global warming in the industrial era is just a natural fluctuation in the earth’s climate, according to a new study by McGill University physics professor Shaun Lovejoy.

The study, published online April 6 in the journal Climate Dynamics, represents a new approach to the question of whether global warming in the industrial era has been caused largely by man-made emissions from the burning of fossil fuels. Rather than using complex computer models to estimate the effects of greenhouse-gas emissions, Lovejoy examines historical data to assess the competing hypothesis: that warming over the past century is due to natural long-term variations in temperature.

“This study will be a blow to any remaining climate-change deniers,” Lovejoy says. “Their two most convincing arguments – that the warming is natural in origin, and that the computer models are wrong – are either directly contradicted by this analysis, or simply do not apply to it.”

Lovejoy’s study applies statistical methodology to determine the probability that global warming since 1880 is due to natural variability. His conclusion: the natural-warming hypothesis may be ruled out “with confidence levels great than 99%, and most likely greater than 99.9%.”

To assess the natural variability before much human interference, the new study uses “multi-proxy climate reconstructions” developed by scientists in recent years to estimate historical temperatures, as well as fluctuation-analysis techniques from nonlinear geophysics. The climate reconstructions take into account a variety of gauges found in nature, such as tree rings, ice cores, and lake sediments. And the fluctuation-analysis techniques make it possible to understand the temperature variations over wide ranges of time scales.

For the industrial era, Lovejoy’s analysis uses carbon-dioxide from the burning of fossil fuels as a proxy for all man-made climate influences – a simplification justified by the tight relationship between global economic activity and the emission of greenhouse gases and particulate pollution, he says. “This allows the new approach to implicitly include the cooling effects of particulate pollution that are still poorly quantified in computer models,” he adds.

While his new study makes no use of the huge computer models commonly used by scientists to estimate the magnitude of future climate change, Lovejoy’s findings effectively complement those of the International Panel on Climate Change (IPCC), he says. His study predicts, with 95% confidence, that a doubling of carbon-dioxide levels in the atmosphere would cause the climate to warm by between 2.5 and 4.2 degrees Celsius. That range is more precise than – but in line with — the IPCC’s prediction that temperatures would rise by 1.5 to 4.5 degrees Celsius if CO2 concentrations double.

“We’ve had a fluctuation in average temperature that’s just huge since 1880 – on the order of about 0.9 degrees Celsius,” Lovejoy says. “This study shows that the odds of that being caused by natural fluctuations are less than one in a hundred and are likely to be less than one in a thousand.

“While the statistical rejection of a hypothesis can’t generally be used to conclude the truth of any specific alternative, in many cases – including this one – the rejection of one greatly enhances the credibility of the other.”

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13 thoughts on “Odds that global warming is due to natural factors: Slim to none”

  1. I also believe that Global warming is due to natural factors. Precession, the Earth’s orbit and inclination have an effect on global warming and just like my Astronomy lecture likes to say “Global cooling”. The Earth’s orbit carries it 1.7% closer to the sun during winter and 1.7% farther during summer enabling Earth weather conditions to fluctuate during winter, summer and other seasons.

  2. Lets go back to the `scientific known/unknown facts ` :
    Ever changing Total Solar Radiant Heat coming towards Earth ; which is clearly correlated with the changing cycles of our Sun since its origination and throughout its Milky Way galactic rotation cycles (similar to well known and documented Sun spot cycles` as well as “OTHER CYCLES” our sun may have we have not even know or measured yet long enough to have reliable data for statistical `variance` . And obvious `natural` events like `volcanic activities` cumulative effects since the beginnings of our planet Earth 4,5 billion years ago as well as `Fermentative` and `Photosynthetic` activities of its Bio mass accumulated over the last 3,8 billion years are obviously fluctuated –up and down- as a result the `Gas composition of out planet` as well as CO2 concentration other gases changed throughout the numerous Ice Ages our planet witnessed since its existence ; as well as well documented Mass Extinction calamities millions of years ago . So CO2 rise and fall has been `innocent by stander` rather than the primary cause since we see very high CO2 concentration periods of our planet`s past (6-7 times ..! present CO2 ) .

    So after this short introduction of serious of past events ; what is all this `Man made accusations ` self incriminating nature ; worldwide propaganda has been going on for the last couple of decades are all about ? it is simply absurd and clearly bad ignorant abuse of science at its worse form .
    Presuming and assuming things – like solar radiant heat coming to earth is FIXED and NOT CHANGING- with only documented available 40 odd years of reliable data is NOT enough to detect the statistical long term `variance` to have any scientific conclusion , add to that we have never ever measured the changing cosmic radiations effects on high cloud formation also .
    And – changing shelter/shadowing(cooling as well as warming) effects from radiant heat – cycles as well as the solar radiant heat cycles we do NOT have data for significantly long periods of time to detect `the variance` .. So scientifically speaking what we say in computer programming ; you input `presumptions` in other words `garbage` as data to the any which computer program you have ; you simply get `another garbage` as output conclusion BUT never the truth you are after ..First you have to have reliable “long term” recorded data rather than barely 40 years and so odd solar radiant heat measurement as well as (* ) changing cycles of Galactic cosmic radiation causing high cloud formation , until than you do not have the `facts` and real `causes` of global warming cycle we are all witnessing . Like preliminary so called `CLOUD` experiment at CERN only 3 years ago at the link which suggest the existence of significant correlation which we had never ever measured as a factor of Global warming event –WE SIMPLY PRESUMED – which is obviously bad science . http://www.nature.com/nature/journal/v476/n7361/full/nature10343.html

  3. I believe that global warming is possibly due to natural factors; similarly to the ‘Ice Age’ being due to natural factors. Instabilities in the amount of incoming solar radiation is the most likely cause of large-scale changes in the Earth’s climate during the Quaternary (period which started around 1.5 million years ago).

    The concentration of heat from the sun is the most likely cause of the glacial cycles. The greater the tilt in the earth on its axis – the stronger the difference in the seasons. The range of motion in the tilt takes place over a period of 41,000 years. This phenomenon is called the precession of equinoxes. This could however, be the reason for global warming as it can be similarly explained in the Ice Age stage.
    Global warming can simply be seen as the opposite of the Ice Age which has been proven to be from natural causes and not man interfering. I do agree that man has sped up the process of global warming with creating industrial areas and letting off harmful products into the atmosphere. In conclusion I still believe that global warming is a natural result to a large extent.

  4. I would argue for a more balanced approach to the challenge of global warming. First of all, let us accept that global warming is a fact and not just some kind of political conspiracy. In my view, too much time, money and energy is wasted on different parties trying to prove or disprove the existance of global warming. Secondly, from the scientific research that has been done, it is clear that global warming is both a result of natural cycles in weather patterns and human activity. If this is accepted, we can move forward more productively.

    While it is important to establish the contribution of nature and humans to global warming, perhaps the time has come to shift the emphasis somewhat to what can be done to counteract global warming. No one can deny all the evidence available regarding the negative effect of carbon dioxide and greenhouse gases on the environment and on human health. The question now becomes: What can we do to address this? More research needs to be done on alternative sources of energy. Cooperation accross borders and disciplines is needed, as well as making funding available. Beware of the day that the egos of activists stand in the way of progress!

  5. Michaela i agree with you. Both natural factors and us humans contribute the warming of the Earth thus we should on both sides, we need to see it this way our carbon emission they does not create global warming it only accelerates the rate.

  6. I strongly believe that global warming with its rapid increase is due to us the human race.

    As we know that the Earth’s climate has been changing through out even during the starting of creation without no inhabitants, but as we humans consider to emit CFCs in our atmosphere we increase the speed of the ever changing climate of our planet. As others have said their points i strongly believe that we need a more ways to solve problems of global warming, as the catastrophe will affect us as the human race.

    Pointing fingers never helps because we end up blaming each other without looking at the main problem. Global warming is coming thick and fast, we need to be up cause this is our problem. Change cannot be stopped but we all can be part of the change whether big or small and whether bad or good.

    This research is on point because it awakes that fossil fuels emission are not good for our ozone and the future of this planet.

  7. To blame the human race for all of the global warming that occurs is quite harsh and I think unfair! Yes, man uses excessive amounts of fossil fuels that increase the rate of global warming and produces more CO2 but global warming would still be taking place. There are also other ways of producing carbon dioxide without burning fossil fuels which Lovejoy doesn’t take into account. Throughout time we have seen climate change whether it bringing warming or cooling as seen with ice ages and the temperature changes have occurred even without the large increase in CO2.also to assume CO2 is the only factor that affects global warming is just impractical. The amounts of carbon dioxide have fluctuated throughout time and cannot be measured as a constant up until humans started increasing that amount.
    This is why I disagree with Lovejoy in saying that global warming I cannot be due to natural factors as well as human factors.

  8. u14179785

    Carbon dioxide is not the only human activity factor that contribute to global warming, Lovejoy could have at least considered other factors such as deforestation,materials used to build houses and industries, alteration of the surface ( filling the surface with concrete), etc, in his hypothesis then in this case we were going to be able to conclude if whether his results are viable not. Also if nature really has an impact on global warming then why is the temperature drastically increasing now in the industrial era than it did in the early age?

  9. I agree that global warming is mostly due to human beings.

    The 2 main factors that worsen global warming due to humans are Greenhouse Gases and carbon emissions, Tett et al. 2000 (T00). These gases and emissions are let off during the production of electricity, by burning coal, oil and natural gas. The emissions that are released warm up the atmosphere which leads to global warming. The heat cant escape due to the ozone layer that surrounds the earth. This leads to ice bergs melting, changes in the weather and many other consequences such as fish not being able to cope in the water that should be colder than what it is due to the earth being warmer than it should.

    Humans worsen the fact that there are carbon emissions in the atmosphere by deforestation. Trees take in carbon dioxide and release oxygen which is a natural way of dealing with global warming. However, when trees are cut down, they can’t absorb the carbon emissions and so the earth gets warmer.

    Although global warming is mostly due to humans, there are also some natural causes. These natural causes include volcanic activity which releases heat, and El Nino (which is when the ocean naturally heats up and droughts occur).

    Therefore, there are natural and human causes of global warming, but the predominant cause is humans.

    Michaela Fyfe 14019753

    • This same thing the `blame game ` had been played thousands of years ago by the ancient priests ; unknowing innocent people in order to manipulate them for their dubious intents , they(ancient priests) tried to convince the people that celestial events are the curse and punishment from Gods for presumed and perceived wrongful deeds done by the people . Human History and its nature never changes only the role players have different names now . Over four billion ( 9 zeros behind the number ) years of Earth`s History this planet have had witnessed so many glacial and interglacial stages – cold and warm cycles- and mass extinctions in between , so many times our solar system rotated around the center of our Milky Way Galaxy BUT every time we manage to find `different explanation and cause ` not much argument involved there ; except this one (Global warming) simply because now we have so many well territorialized Nation States competing for cheaper energy production and competitive edge of course Global Energy Politics has large stake here obviously to change and manipulate the traditional energy production characteristics . Nothing will be able to change the direction or the destiny of Global Warming at the end of course , simply because human beings are not able to change or effect the Climate no matter what they do – they are not the underlying cause of it – ; they have to adjust to the change rather than hopelessly trying to `stop or slow down ` the ultimate course of events by blaming each other ; as the Climate changes as it had happened for billions of years up and down before ; and all living things – had evolved and adapted accordingly as the climate changed- we will do that too . Future generations will look at todays `debates and mutual blames` and `laugh at our ignorance and lack of knowledge and incompetence and misunderstanding the reality of our planet earth over 4 billions of years and it`s changing and ever adapting life forms to it`s dynamic climate ` .

  10. Lovejoy’s analysis is deeply flawed. First, going back only 1500 years is inadequate, since longer warming and cooling cycles reveal significant variation that contradict his assumptuons. Second, using CO2 as a “proxy” for industrial activity is flawed. Carbon dioxide has fluctuated over regular periodic cycles. And while CO2 correlates with warming, it comes hundreds of years after warming, not before it! It is thought that this comes about because the oceans act as a tremendous sink for CO2. These facts undermine the use of CO2 as a proxy for human activity.

    As they say about models and statistics: garbage in, garbage out.

    • Well said Todd ; to any which program you like `You put the garbage in as data , obviously you get `the garbage conclusion` out as data ` no other way around indeed …What is important is NOT only the program design but the accuracy of the `collected input data` , any Retrospectively Designed Computer Program if they ignore the `SUN`s radiant heat` coming towards the Earth over a long periods of time rather than merely 40 years is ? `flawed` simply they are not putting `any real long term reliable data from the only heat source we ever had -THE SUN- .. Wild retrospective assumptions are NOT DATA …they have never been ..

  11. Here we go again `blaming humans for excessive fossil fuel` use fundamentally and scientifically wrong assumption :
    First ; the fact is `The Climate of this planet Earth of ours ` has always changed in both ways – colder or warmer – since its creation over 4 billions of years –never ever stayed the same .
    Second ; you do NOT KNOW the things listed below …
    (UN Panel on Global Warming) never ever calculated the radiant energy(heat) fluctuations over a “significantly long run” coming from our only real heat source the SUN ( Simply because they did not have the technology to measure it far back even 40 years and they do NOT HAVE DATA significantly long time interval at all …! ) and they have to ASSUME (Wrongfully) that the amount of heat coming from SUN is `FIXED ` and NOT CHANGING ? or FLUCTUATING ? according to galactic (Milky way) cycle . By the way they never calculated the effect of changing galactic cosmic radiation over a reasonable long period on stratosphere high altitude cloud formation and its effects on atmosphere and global temperature also …
    Without knowing the NATURE and CHARACTERISTICS of the ONLY REAL HEAT SOURCE WE (OUR EARTH) HAVE `THE SUN` how can you assume things related with `temperature on earth` ?….
    For the final punch line ; just look at the period so called “Little Ice Age “ http://en.wikipedia.org/wiki/L… AD 1550 and AD 1850 whopping 300 years of unexpected / unusual Global cold period …. You see lots of gaps and un answered questions with this so called `man made global warming`, what cooled the Earth like freezer havens sake for 300 long years between those years ..? The logical answer was THE SUN most agree almost unanimously even they backed up with lots of data about solar effects of this little ice age period …
    So when the whole Earth Cools most logical answer was the Sun (Nobody ever dared to say people of 1550 AD STOP BURNING COAL or FOSSIL FUELS FOR 300 YEARS so the CO2 DROPPED and the whole world had Little Ice Age … BUT as you clearly see when whole Earth start warming up THAN the CAUSE IS MAN MADE ..! but NOT the SUN ?…

    I bet you got the idea what I am trying to say here …Believe me the common sense and pure logic states that the SUN `Cools us as well as Warms us` that is the obvious answer here … Forget about so called CO2 that is simply a `Man made Politics of Global Energy `… CO2 is just an Innocent Bystander but not the real cause of Global Warming and never was ..

    Thank you

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