Have the Last Four Summers and Winters Felt Warmer?

During a congressional hearing in 1988, Goddard Institute for Space Studies climatologist James Hansen predicted that a perceptive person would be able to notice the climate was changing by the early 21st century. Has his prediction panned out? He digs into the topic in a discussion published this week on his website.

The short answer: yes, depending on where you live, you should be able to tell that in the last four years, for example, summers have been warmer than average. The last four winters have also been noticeably mild in most parts of the world. (Though it’s worth noting that the last two winters in the continental United States have actually been cooler than average).

Read on below to see how Hansen explains it in more detail. (I’ve excerpted some of the more accessible sections of the text and two graphs, but the full discussion is available here as a pdf.)  More context and details about trends in the global surface temperature record are also available.

This past winter, for the second year in a row, seemed pretty extreme in both Europe and the United States. So this is a good time to check quantitatively how seasonal climate change is stacking up against expectations.

People’s perception of climate change may be the most important factor determining their willingness to accept the scientific conclusion that humans are causing global warming (or global climate disruption, as you please). Itis hard to persuade people that they have lying eyes.

In the paperattached to my congressional testimony in 1988 (1) we asserted that theperceptive person would notice that climate was changing by the early21st century. Now we can check the degree to which the real world has lived up to this expectation. The answer will vary from one place to another, so let’s make a global map for this past winter. Each gridbox will be colored red, white or blue, depending on how the local temperature this past winter compared with the categories established by the 1951-1980 climatology.

Figure 7 (above) shows the result for the last four winters (summers in the Southern Hemisphere). To make the maps even more useful we use dark blue and dark red to show those places in which the temperature fell in the extreme (>2 standard deviations) category that occurred only a few percent of the time in the period of climatology1. The extreme cases are important because those are the ones that have greatest practical implications, especially for nature. Species are adapted to climate of the past, so a change to more extreme climates can be detrimental, especially if it occurs so rapidly that species cannot migrate to stay within tolerable climatic conditions.

The numbers on the top of the maps are the percent of the area falling in the five categories: very cold, cold, normal, hot, very hot. In the period of climatology those numbers averaged 2%, 31%, 33%, 31%, 2%, rounded to the nearest percent.

Figure 7 reveals, for example, that the past two winters in Northern Europe both fell in the category of “cold” winters, but not extreme cold. The area hot or very hot (51-73%) far exceeded the area with cold or very cold conditions in all four years (14-27%).

Figure 8 (top) shows results for Jun-Jul-Aug for each of the past four years. In both Jun-Jul- Aug and Dec-Jan-Feb it is apparent that the area falling in either the hot or very hot category totals 64-78% in agreement with our 1988 climate simulations.

The perceptive person who is old enough should be able to recognize that the frequency of unusually mild winters is now much greater than it was in the period 1951-1980. But mild winters may not have much practical impact. So a return to one or two colder than average winters may affect the public’s perception of climate change.

On the other hand, the huge increase in the area with extremely hot summers, from 2-3% in 1951-1980 to as much as 30-40 percent in recent years and most of the land area in 2010. If people cannot recognize that summers are becoming more extreme they may need to have their senses examined or their memories. Perhaps the people who do not recognize climate change are living in air-conditioned environments, which are restricted mainly to one species.

–Adam Voiland, NASA’s Earth Science News Team

14 thoughts on “Have the Last Four Summers and Winters Felt Warmer?”

  1. Thats not what the big corporations and the republicans on the hill are saying. Are you saying they are lying to us?

  2. Attempts at forecasting climate change based on questionable past temperature data is reserved for crystal ball pyschics or arrogant, publicity seeking NASA scientists!!

  3. Interesting data, but has anyone compiled a similar analysis for a longer period? Say, standard deviations for 1990 to 2010? Four years is an awfully short period to use to draw long-term conclusions.

  4. I was born in New Jersey in 1958 and have lived most of my life here. When I was in my teens car and motorcycle races on Greenwood Lake 20 or so miles north of here, were a regular event during the winter. When I was in my teens, it was common to have nights well below zero degrees F in February. During the summer, it rarely got over 100 degrees F.

    None of these things is true anymore.

    The Forsythia around here used to be in full bloom near the end of April, right around my birthday. They are ready to bloom now, three weeks earlier.

    In autumn, the trees don’t get anywhere near as brightly colored as they used to. Now, they sort of change color and many leaves simply turn brown on the branch.

  5. You’re not seriously suggesting that it’s sound science to ask people if they feel it’s been warmer over the last four summers?

  6. Absolutely not!
    The past three summers have been awful, the one before was surprisingly cool compared to the beautiful one before it.
    Past three years MUCH cooler and wetter than normal.
    Cooler temps in July and Aug are not the norm in this neck of the northern hemisphere.
    Near Ottawa Canada.
    I hope the sun to revs up big time, before the fools burn all the food for vehicle fuel when uncounted amounts of oil, gas and coal are in the ground. It’s not limited its just not political accessible because of lies and damn lies.
    Think about this, our hydro bills have tripled, my water is now being charged for, got kids in college and you still expect us to ‘rinse, clean’ and recycle glass, plastic and etc.? I can’t afford to pay increase in food, fuel and utilities for some third world country’s tyranical ruler to force their citizens to burn our plastic to make cheap plastic pellets for China to sell us cheap plastic bobbles, and these people are paid pennies per day to work in toxic environments? Containers that I purchased to consume contents, paid more tax on and now pay MORE to clean it, more gas costs to get it home…blue box is not being replaced by our home this year. (they usually get broken in winters as the cold temps snaps the thin plastic)not happening anymore from our house.
    Bio-fule is as much of a pollutant as gas BWT, if not then why won’t the airline industry adopt it then? Be a huge profit margin for them to capitalize on if it were truly viable. AND in this area, the bio vehicles need to be plugged in all winter. Where as our gas ones don’t but for the nights it’s -20c or colder.

    Hope this is not a real scientic poll however given the hysteria about the weather and the greedy ones trying to profit from it, I would not be surprised.

    Wish the real scientists were here…

  7. I don’t know about this. Maybe it’s true in the USA, but Australia just finished summer a few months ago and both I and others agree we didn’t have anywhere near as many scorching hot days as we have had in the past.

  8. When I was a young child in the early 1960s here in Pittsburgh, I remember that I was able to play outside with my Christmas toys many years. My late mother would say that it always snowed for Russian Christmas, and she was usually right. It would snow in January, rain in February, then the lilacs would bloom in March and April. Summers were warm, but my parents never felt the need for air conditioning until they became elderly.

    This year, winter began at the beginning of December, and it hasn’t been warm or dry enough to start riding the motorcycle to work yet.

    It’s my personal belief that if World War 2’s manufacturing, and that of the early Industrial Revolution, didn’t alter the Earth’s climate then nothing will. Think about it…there were absolutely no environmental controls on any process anywhere in the world…acrid smoke spewed into the sky, poisonous pollutants spilled unabated into the rivers and onto the ground. We’ve spent the last 40 years cleaning up junk that in some cases pre-dates the Civil War.
    And still it’s not enough…people routinely write to the papers and complain about how American industry and power generation is “murdering” their children.
    These people have no memory of when the streetlights were on at noon, or how “moonscapes” where nothing grew were in close proximity to virtually every industrial facility, and how Pittsburgh still struggles to free itself of the “hell with the lid off” tag.

    In my 56 years, I never saw the streetlights on at noon, but I did see the moonscapes. We’ve come a long way since then.

    Our area recently attained EPA compliance for fine particulates; the EPA’s response was to tighten the standards, move the goalposts, and keep our area in such a non-compliance noose that even if everyone went on welfare pollutants blowing in from China would cause the area to be in violation.

    You don’t have to be a rocket scientist to see a pattern here.

    When it comes to the true science of climate change, I trust a geologist before I trust anyone else. The record of the rocks tells those who are not blinded by an agenda that climate change on Earth is continuous and never stops. For instance, the record shows that at one time there were no icecaps and the oxygen content of the atmosphere approached 40%.

    There are a lot of people out there who only want to sit home and collect Government checks while driving their foreign-made hybrid cars to Wal-Mart. They think that electricity can be imported from China like everything else they buy.
    There are also a lot of people who want to force everyone else to follow their chosen agenda.

    Rampant speculation in fossil fuels will drive their prices to the point where use drops sharply and it becomes too expensive to operate anything that uses petrochemicals or combustion.

    Educate yourselves. Read the geological records. If it was warm enough on Earth that there were no icecaps, how warm was it on Mars during the times that the Earth was covered with lush vegitation and huge exothermic animals roamed the planet?
    What caused the last Ice Age, and what happened to many of the animals that lived then?

    Like it or not, change is the only true contant in this life and universe.

  9. Vehicles and Nucular plantsthat expel heat are part of Global Warming too.Its seldom talked about!

  10. Superb post and its really interesting. You done a great job please keep it. Thanks.

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