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Are humans too insignificant to affect global climate?

What the science says...

Select a level... Basic Intermediate

Humans are small but powerful, and human CO2 emissions are causing global warming.

Climate Myth...

Humans are too insignificant to affect global climate

To suggest that humanity is capable of impacting and disturbing forces of such magnitude is reflective of a self-centred arrogance that is mind numbing. Humanity is a subset of Nature. Nature is not a subset of humanity. We have travelled full circle. We are back in the mindset that prevailed when Society’s leaders dictated what people in Copernicus’ days may or may not think. The Earth is once again flat. (source: Financial Sense University)

When we experience weather events like hurricanes and floods, it’s very easy for us to feel insignificant and powerless in the face of such massive natural forces. How can humans influence this? Well, yes, we can. Of course we can’t influence a single weather event, but we can and do have a long term influence on the climate that causes it.

Since the industrial revolution, with ever-increasing supplies of fossil fuels, the activities of a dramatically expanding world population have made significant alterations to the make-up of our atmosphere.

In some cases human-caused change is direct and unambiguous. The harmful effect of the human release of CFCs on the ozone layer is well documented and not disputed. Down on the ground, draining of marshland and deforestation can produce a significant decrease in water vapour in the atmosphere downwind; while the introduction of irrigation for agriculture has the opposite effect. Over time, both of these human activities can alter patterns of rainfall, turning deserts into green areas and green areas into deserts.

In other cases the human causes of climate change are more complex. Emissions from cement production, pollution and the release of particulates to form smog in the atmosphere, all affect climate.

Without doubt the most significant of all the human causes of changing climate is the dramatic increase in CO2. After remaining relatively steady for the last 650,000 years or more, in just the last two hundred years the concentration of CO2 in the atmosphere has suddenly shot up from 280, to more than 380 parts per million. And it’s still rising. This dramatic 30% increase has all taken place at the same time as humans have been burning fossil fuels at a greater and greater rate.

Of course there are also natural sources of the CO2 in the atmosphere, such as vegetation, but fortunately there are differences that scientists can measure between the CO2 derived from fossil fuels and the CO2 derived from plants. The changing concentrations of the two types demonstrate that the additional CO2 can only be the result of human activity.

This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric CO2 has increased since the Industrial Revolution. (Credit: Vostok ice core data/J.R. Petit et al.; NOAA Mauna Loa CO2 record.)

Of course, as CO2 is the most common of greenhouse gasses, the additional concentration is what causes most of the rise in temperature. This is resulting in a change in weather patterns and ocean currents; the melting of global ice formations; and an increase in extreme weather events.

So, yes; though we might be pretty helpless when it comes to controlling the weather, humans are certainly capable of changing the world’s climate.

Basic rebuttal written by John Russell

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial


Last updated on 30 November 2015 by MichaelK. View Archives

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Comments 26 to 34 out of 34:

  1. Teacher:

    I am not impressed with  They treat conclusions made by tens of thousands of scientists as equal to the opinion of a single person who is paid to speak by the fossil fuel industry.  The data shows that over 95% of scientists who study climate are convinced humans cause climate change.  If you present equal amounts of scientific arguments with con arguments that are fake you will convince your students that a debate exists when there is none.  The students will not be able to identify the fake con arguments.

    In 1965 President Johnson asked the National Academy of Science, the top science organization in the USA, if Golbal Warming was really a potential problem.  They replied that it would be a big problem in the near future.  That future is now.  The conclusion had been made already in 1965.  Pro/con is confusing the public, your students, by acting like there is a debate when none exists.  That is the entire point of deniers: to act like there is no scientific conclusion.

    Check the sources of all the con arguments.  15 scientists here (how many were really climate scientists, or were they computer scientists?), a single article published in an obscure Chinese journal there, a retired physicist who has never studied climate is quoted as if he was an expert.  This is posted as equal to the IPCC report that thousands of experts wrote and every government in the world, including the USA, agreed was the actual state of the science.

    Pro/con needs to screen their arguments.  They are claiming that 10=15,000.  They give equal weight to the IPCC, which has thousands of experts from the entire world, and the Heartland institute, which is a fossil fuel funded organization with less than 10 climate scientists.

    In my class I found that graphs of data were best accepted by students.  They tended to disbelieve any written material regardless of the source.  Be careful to get your graphs from reliable sources.

  2. Teacher @23 ,

    it is important, indeed essential, for students to see the OHC [Ocean Heat Content] graph showing the accumulating heating of the planetary ocean.  The ongoing warming of the ocean (which absorbs over 90% of the accumulating heating caused by the higher levels of greenhouse gasses) is a matter which demonstrates the falsity of the various "Con" arguments listed at the ProCon website.  Add to that, the melting of permafrost and the rapid decline of the planet's glaciers, the loss of Greenland land-ice, etcetera etcetera.

    I appreciate that the ProCon website is obliged to present a list of "Con" arguments — but really, all those Con arguments are not-at-all science-type arguments but are almost entirely lawyer-style arguments (presenting deliberately misleading & cherry-picked points — and many of them self-contradictory and lacking in probity.   Many are also ludicrous : e.g. note the comment: <the recent global warming period of the 20th century is the result of a natural 21-year temperature oscillation, and will give way to a new 'cool period in the 2030's. '> 

    Presumably such nonsenses serve as discussion points for teachers to present for students' consideration . . . but I would have thought that the teaching curriculum would be so crowded, as to preclude much time being allotted to the study of scientifically-fake statements.  To me, it seems unfair that teachers should have to develop a considerable depth of climate-science understanding, in order to be able to rebut all the nonsense.   "ProCon" ought to present only valid Pro arguments and only valid Con arguments.  Which would leave a greatly-reduced Con list indeed!!   All the first 12 Con points would disappear, and just Argument #13 would remain — and #13 is exceedingly weak, because Global Warming is merely in the early stage so far.

  3. Teacher @23 , 

    a further small point which might be of interest to American students :-

    the once-marvellous Glacier National Park is nowadays sadly depleted compared with its former condition.  By the end of the century, the Park will need to change its name to something entirely different, it seems.

  4. Hmm. The extremely tricky bit is how are 7th graders going to evaluate the reliability of source information? With so much misinformation, misrepresentation of science, and downright false information out there from motivated reasoners, it is a minefield to navigate. Even limiting to "peer reviewed" research is complicated by predatory journals. This website delivers good guidelines but 7th graders just dont have those skills. For that matter, many gradutes dont have/use those skills. Everyone of us is prone to motivated reasoning.

    To my mind, what 7th graders need to know is what the scientific consensus is.

  5. Thanks for taking the time to respond and to give me advice everyone. I definitely have a more detailed lesson plan and more graphs for students to analyze. 

  6. As has been stated above, I truly appreciate the respectful tone with which the commenters have been making their arguments and asking questions. It’s a refreshing change to be able to sort through information without being hit over the head with politics. 

    I have a lingering question that I hope someone can address or provide a theory about. Since the earth has been in many states over its 4+ billion years of existence - having had several ice ages and heat waves that thawed the landscape and made life possible - how does one account for/explain the other major climate shifts, given there were no humans around to make an impact? How can we be so certain that our actions alone are dooming is, rather than it just being another temperature or climate change cycle of our very active planet? 

    This is a serious question that has always plagued me when discussing this issue. I hope to get some feedback from this well-informed group. 

    Thank you in advance- 

  7. Duke @31 ,

    first go back to basics.  The major factors determining the Earth's climate are :-

    1.  The insolation: level of shortwave energy coming from the sun.

    2.  The level of Greenhouse Gasses ~ most significantly, CO2.

    3.  The level of aerosol particles reflecting sunlight.

    During the past almost 1 million years, the "Milankovitch cycle" of slight Earth axial & orbital changes has initiated/triggered a half-irregular series of glaciations & (briefer) de-glaciations.  Currently we are on a gradual downward path of cooling (of about 5,000 years' duration) . . . and with more cooling still to come for 20 or so millennia.  Or at least, that was the path, until recent events of the past 2 centuries.  (Please note that the so-called Little Ice Age and the Medieval Warm Period have been fairly minimal wiggles on that long-term cooling background.)

    However, against this background pattern of cooling, there has been an extraordinary (and continuing) upward spike of global temperature during the past 100 - 200 years.  What has caused this remarkable change?  #The analogy might be: a small-town police chief is used to seeing 3 - 6 house burglaries per year . . . but now he has just had 80 burglaries on one weekend ~ so, obviously, there's been a drastic change of some sort, and he has to figure out what has caused the extraordinary change.

    For the scientists, they have to figure whether the rapid/huge temp spike ( currently about half a degreeC above the warmest level of the Holocene's previous 10,000 years ) has been caused by changes in insolation and/or GHGasses and/or aerosols.  ( Other causes: cosmic rays, cloud changes, etcetera, have been checked out . . . and are clearly not a contributing factor in the climate change. )

    Duke, you probably know most of that.  And the evidence points to a single "culprit" for the spike.  #Though I'm not sure what you mean by "dooming" ~ after all, the present & future consequences of global warming are 95% bad and 5% good (which is kind of okay for those in the 5% category!)

  8. Duke @31,

    You mention "4+ billion years" and for much of that time the Earth's climate is little understood. So perhaps a few words about climate prior to the ice-age/interglacial cycles of the last 3 million years.

    The speculation for the very early ages is that there had to be a very strong greenhouse effect because the Sun was much fainter and there had to be liquid water for life to evolve. So that is all very tenuous stuff.

    It is perhaps the last 500 million years that the geological record remains complete enough to have a good stab at global climate. I say "stab" as, for instance, the gaphic below taken from Wikipedia only provides a relative  δ18O record. (A long-term trend has to be subtracted from the data. Here an imprecise method is used and that means δ18O levels (temperature) more than 100 million year apart start to become difficult to directly compare.) So the wobbles are there but the relative maxs & mins should not be compared.

    Phanerozoic d18O

    Research suggests causes for the various wobbles. For instance, the Ordovician-Silurian glaciation (450My bp) is seen as resulting from the erosion of large fields of volcanic rock that proved particularly good at sucking CO2 from the atmosphere. By modern standards, CO2 levels were still sky-high but the Sun was much weaker, requiring something like 4,000ppm CO2 to give a modern global temperature.

    But note such wobbles were very slow compared with today's AGW, these ones being measured in millions of years. Others measure in tens-of-thousands of years, as do the recent ices-age/interglacial transitions.

    And none of this research would make any sense whatever without CO2 as a greenhouse gas and the present human-caused rise being a serious climate-changer.

  9. Should add to Eclectic that nothing special about earth in respect. You can calculate the surface temperature of any rotating planet, around any sun, knowing solar insolation at top of atmosphere (simple calculation from solar output and distance from sun), atmospheric composition, and aerosols.  (Of course assuming that laws of physics dont vary with space and time).

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