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Hansen Knew Why The 1930’s Were Warmer (Before He Adjusted Them!)

December 22, 2013

By Paul Homewood



1999 Version

2013 Version



In 1999, James Hansen still believed that US temperatures were much higher in the 1930’s, than in the 1990’s. This was, of course, before he adjusted all his figures to prove the opposite.

What is interesting, though, is that he actually knew why the USA had cooled since the 1930’s. From a paper he wrote in 1999, “Whither US Climate”:


What’s happening to our climate? Was the heat wave and drought in the Eastern United States in 1999 a sign of global warming?

Empirical evidence does not lend much support to the notion that climate is headed precipitately toward more extreme heat and drought. The drought of 1999 covered a smaller area than the 1988 drought, when the Mississippi almost dried up. And 1988 was a temporary inconvenience as compared with repeated droughts during the 1930s "Dust Bowl" that caused an exodus from the prairies, as chronicled in Steinbeck’s Grapes of Wrath.

How can the absence of clear climate change in the United States be reconciled with continued reports of record global temperature? Part of the "answer" is that U.S. climate has been following a different course than global climate, at least so far. Figure 1 compares the temperature history in the U.S. and the world for the past 120 years. The U.S. has warmed during the past century, but the warming hardly exceeds year-to-year variability. Indeed, in the U.S. the warmest decade was the 1930s and the warmest year was 1934. Global temperature, in contrast, had passed 1930s values by 1980 and the world has warmed at a remarkable rate over the last 25 years.

A picture of how U.S. climate change during the past half century compared with the rest of the world is shown in Figure 2. This map shows that the trend has been toward warmer temperatures in most of the world. There has been nearly ubiquitous warming in the tropics, especially in the Eastern Pacific Ocean, where the largest warming coincides with the location of more frequent strong El Niños. The strongest warming has been in Alaska and northern Asia. Warming in Alaska is often associated with El Niños. A suspicion of many climatologists — as yet unproven — is that an increasing greenhouse effect may cause more frequent and intense El Niños. Asia has long been predicted to show the largest warming due to increasing greenhouse gases, especially in the winter, and observations are consistent with that.

Yet in the U.S. there has been little temperature change in the past 50 years, the time of rapidly increasing greenhouse gases — in fact, there was a slight cooling throughout much of the country (Figure 2). We caution that linear trends, as in Figure 2, can mask temporal detail. Indeed, Figure 1(b) indicates that the last 20 years have seen a slight warming in the U.S. Nevertheless, our analysis (Hansen et al., 1999a), summarized in Figures 1 and 2, makes clear that climate trends have been fundamentally different in the U.S. than in the world as a whole.

Is this a temporary fluke, a chaotic regional climate fluctuation? If so, as the regional fluctuation reverses and global warming continues, will the U.S. experience dramatic, perhaps "disastrous" climate change in the next few decades? Or is there an understandable and continuing reason that the U.S. is warming less than the rest of the world? In that case, will the U.S. be relatively immune to global warming in the next several decades?

In order to answer such questions and predict future climate change reliably, a prerequisite is an understanding of the cooling of the past half-century in the U.S. Figure 2 suggests that the U.S. cooling is associated, at least in part, with cooling in the North Atlantic Ocean. Climate model simulations tend to confirm this, yielding cooling in the U.S. during the past 50 years when driven by observed ocean temperatures (Hansen et al., 1999b).

But that only changes the question: what is the cause of the Atlantic cooling? In part, the Atlantic cooling is a natural fluctuation, the North Atlantic Oscillation, that occurs on decadal time scales. Observations of the past few years, summarized in Figure 17 of Hansen et al. (1999a), suggest that the North Atlantic Oscillation is now moving into its warmer phase.

However, North Atlantic cooling is also a predicted consequence of the transient growth of greenhouse gases. Climate models (Manabe and Stouffer, 1995; Russell and Rind, 1999) driven by increasing greenhouse gases yield increased precipitation at high latitudes, decreased ocean salinity in the North Atlantic, and thus a weakening of the ocean conveyor belt that transports heat to the North Atlantic.

Additional mechanisms may contribute to observed climate change. For example, in the decades after World War II, when the amount of aerosols (fine particles) in the air grew most rapidly in the Eastern U.S., the pattern of cooling showed a clear resemblance to the distribution of aerosols. Also changes of solar irradiance (the brightness of the sun) are difficult to dismiss as a mechanism of climate change, because there are observed correlations of solar variability and climate change.

The upshot is that we will be able to understand climate change well only with the help of global climate models that are able to incorporate all of these mechanisms on an equal footing. We will be able to test our understanding during the era of satellite measurements, when all of these forcing factors can be measured accurately.



So, when he claimed to know why the US had cooled, was he lying or simply incompetent?

  1. Ben Vorlich permalink
    December 22, 2013 6:27 pm

    If this “So, when he claimed to know why the US had cooled, was he lying or simply incompetent?” wasn’t a rhetorical question then I’d say both.

  2. December 22, 2013 6:44 pm

    I think he was telling the truth back then and is lying now as his agenda has change from science to money and fame but now everyone thinks he’s a crank so who cares.

  3. catweazle666 permalink
    December 22, 2013 7:46 pm

    “was he lying or simply incompetent?”

    Both, of course.

    And greedy.

  4. Sparks permalink
    December 22, 2013 8:11 pm

    The modus operandi of James Hansen is very obvious, considering that he has been in the public eye for a long time (about 46 years?) and has made many statements on earths temperature variability of both warming and cooling, which has indeed changed over time. But one key point of his crank theory has remained constant and that is, what ever state the climate is in, it was and is controlled by human behavior.

    James Hansen believes humans are the cause of “climate change” and the cause of global warming, he is very deceptive in the language he uses when describing “anthropogenic global warming” or “man made climate change” by always referring to it as “climate change”, dropping the “anthropic” part of his crank human controlled climate science.

    James Hansen recently suggested that ~ Maybe Coal Emissions Are Cooling the Planet …

    Enough said!! 🙂

    • March 29, 2016 1:36 pm

      No one is going to know for decades to come if then. We only know the past and measurements were not recorded like they are today but either way, there were periods of Palm Trees growing on a warm Arctic Coastline year-round and other times ice ages so harsh, Great Lakes were created. Then smaller extremes such as 1350-1500 warmth with reversal to mini ice age of Elizabethan Times to warming then that cooling in early 1800s America. Majority was pre-humans and later pre-Industrial age with just the last hundred years of industrial age yet climate is not static. It changes with or without humans. It does have small phases each century that last about 30 years give or take so there are 3 or sometimes 4 per century warm to cold back and forth. Since these are nature and nothing caused by humans, I wonder other than City Heat Island what humans who are actually natural to earth too cause. Pollution yes which is harming humans and other animals but climate tends to have one big player which is the Sun and no one can control that.

      I think data by the 2030s will be helpful to see how climate is 2016 to 2030s compared to past since we are now due for a cold phase that either comes or doesn’t. Whatever the case, I just hope children are safe into middle age pertaining to climate, pollution and all that. We are all okay the next ten years but a planet too hot or cold means humans have to move. Vikings came over at a time when there was no arctic ice by boat. Other times there were land-bridges of ice so there were movements of humans. How do humans make such drastic moves now in drastic numbers if needed? What do you think about all this? You seem to be really smart going by your post.

  5. December 23, 2013 12:38 am

    in the 30’s wasn’t warmer, or colder than today. It just happens that last century almost every decade was ”predictions” for warmer or for ice age is around the corner. Hanson obviously knows the reliability in past ”predictions” and had chosen to ignore the lot:

  6. Brian H permalink
    December 23, 2013 1:36 am

    But still derives all from GHG growth, attributing cooling to dilution of the NAtl. with meltwater, slowing the “conveyor”. Also not as observe, AFAIK.

  7. Brian H permalink
    December 23, 2013 1:37 am

    typo: as observed

  8. December 23, 2013 3:35 am

    H. H. Lamb also changed his position when he set up the Climate Research Unit at the University of East Anglia. He abandoned his own research into natural climate change and adopted the AGW hypothesis without much evidence, if any.

    People don’t read or cite his early work much, but the evidence of his switch is all there to see.

    Wikipedia has some of the history here:

  9. December 24, 2013 12:17 am

    Frederick, Hubert Lamb in the 70’s was promoting ”Nuclear Winter for year 2000, because of the CO2 dimming effect”; which was another con.

    Now the building in East Anglia university where the ”climatologist” are, is called ”Hubert Lamb Building”

    Climatology is voodoo science

  10. Rick Kooi permalink
    July 10, 2015 2:13 pm

    Gavin Schmidt, a climatologist with NASA’s Goddard Institute for Space Science. He also publishes the blog, one of the more-respected climate science blogs.

    “You’ve got true facts,” Schmidt said of the Galileo Movement’s pamphlet. “They’re just not the relevant facts.”

    The pamphlet’s claims about climate science are not new: They’ve been well honed over several years’ worth of debate, and there’s a wealth of information on the web debunking the so-called “denialist” movement’s arguments.

    Here’s a sampling of the Galileo Movement’s facts and an assessment of how they stack up against the body of Earth and atmospheric science, based on an investigation by of several science sources.

    Claim: CO2 is Nature’s colorless, odorless, tasteless gas essential for all life on Earth. It’s not toxic. It doesn’t make land, water or air dirty or unsafe to use. It does not cause disease.

    Claim: CO2 comprises less than 0.04 percent of the air.

    Assessment: True but irrelevant in the global warming debate.

    Nitrogen, oxygen and argon together make up close to 100 percent of the atmosphere. But all three are invisible to incoming “short-wave” radiation from the sun and outgoing “long-wave” radiation from the Earth’s surface. They play no role in regulating the planet’s atmospheric temperature.

    But carbon dioxide and other trace gases in the atmosphere do absorb the outgoing long-wave radiation.

    So while their concentrations are miniscule, their effect is anything but: If the atmosphere didn’t have those trace amounts of greenhouse gases, New York City would be covered in ice sheets – not sweltering – on a typical summer afternoon. The globe’s average temperature would be almost 60 degrees Fahrenheit lower.

    Similarly, toxicity is not an issue in the climate change debate. Yes, crops need CO2. Breathing a little more of it while out on the links won’t impair your golf game. But earlier findings that suggested higher CO2 levels could increase crop yields have been disproved by recent research showing that other nutrients are more often the limiting factor.

    The relevant questions for climate science are how CO2 changes atmospheric temperatures and circulation and alters the oceans’ chemistry and heat capacity.

    Source: Scott Mandia, State University of New York, Suffolk

    Claim: CO2 stays in the air only five to seven years, possibly less than 12 months before Nature cycles it into plants, animals and oceans.

    Claim: Of Earth’s annual production of CO2, humans produce just 3 percent.

    Assessment: True but misleading.

    In this case, the claim confuses residence time of individual molecules in the air with the much longer perturbation to the whole system.

    Carbon dioxide is continuously cycling among the earth, plants and animals, the atmosphere and the ocean’s surface, with the deep ocean serving as a gigantic long-term reservoir.

    Up until the last two centuries, this carbon cycle had been in close balance for the last 10,000 years. But society has pushed atmospheric carbon dioxide levels from 278 parts per million at the start of the industrial revolution to 392 parts per million today, a 40 percent increase.

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    What’s more, the bulk – some 57 percent – of carbon emitted from tailpipes and smokestacks is not even in the atmosphere. It has cycled into the ocean, and scientists generally agree that most of our carbon emissions will ultimately come to a rest in its deepest depths. But that will take centuries. In the meantime, those extra CO2 molecules will slosh around from earth to atmosphere to upper ocean and back, absorbing energy, acidifying the seas and changing the planet in profound and potentially unwelcome ways. In other words, CO2 emitted today will still be impacting the planet for hundreds of years.

    Source: Fortunat Joos, University of Bern, Switzerland

    Claim: Measurements reveal that CO2 levels are a consequence of temperature, not the cause. Temperature drives CO2 levels.

    Assessment: True before 1800. But false today.

    Some 800,000 years’ worth of ice core records indicate that temperature rises did drive an increase in CO2 levels. But that was before humans started digging up huge quantities fossil fuels and transferring all that sequestered carbon to the atmosphere.

    It is worth noting, however, that even in the past CO2 had an impact on temperatures, given its role as a greenhouse gas.

    It’s also worth noting that ancient temperature and CO2-level changes happened over thousands of years. The Earth needed, for example, 5,000 years to bring atmospheric CO2 concentrations up 80 ppm after the last glacial period.

    With the onset of industrialization, the tables turned. Humans have increased atmospheric CO2 levels almost 80 ppm in just 60 years. Now humans are the drivers of CO2 level, not temperature.

    And what frightens climate scientists is that temperature hasn’t caught up yet.

    Source: NOAA Mauna Loa Observatory

    Source: Scott Mandia, State University of New York, Suffolk

    Source: Eric Steig, University of Washington

    Claim: In every 85,000 molecules of

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