Earth Matters

Four Graphics (and a Book) that Help Explain Climate Change

January 25th, 2016 by Adam Voiland

(Image by NASA Earth Observatory)

Though blizzards and cold snaps may have made you forget the news from last week, 2015 was the warmest year in NASA’s global temperature record, which dates back to 1880. During a January 2016 press conference (see the slides here), Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, explained that 2015 was 0.87 degrees C (1.57°F) above the 1951-80 average in the GISS surface temperature analysis (GISTEMP), one of four widely-cited global temperature analyses.

The statistical record is notable, but keep in mind that this year is just part of a much longer story about the climate. If you want to learn more about climate science as a whole rather than just the latest headlines, here are a few resources that you may find informative. The list is not comprehensive (and we are open to more suggestions), but it is a useful starting point for understanding climate science.

Screen Shot 2016-01-20 at 5.41.02 AM

(Image by Eric Roston and Blacki Migliozzi for Bloomberg Business)

The plot above comes from an interactive graphic called “What’s Really Warming the World?” Put together by Eric Roston and Blacki Migliozzi of Bloomberg News (with assistance from NASA climatologists Gavin Schmidt and Kate Marvel), the chart does an excellent job of breaking down the various factors (greenhouse gases, aerosols, solar activity, orbital variations, etc.) that affect climate. It parses out visually how much each factor contributes. The bottom line: greenhouse gases are absolutely central to explaining global temperature trends since 1880. The screenshot above hints at what the interactive looks like, but I highly recommend heading over to Bloomberg to see the full graphic.

Another invaluable graphic for understanding climate change is the “radiative forcing bar chart” below. (You can read an interesting post by Schmidt that explains how these charts have evolved over the decades). At first glance, the chart from the fifth assessment report by the United Nations’ Intergovernmental Panel on Climate Change may seem technical and difficult to understand. It is. But it is well worth looking up the technical terms.


(Image by the IPCC for the WG1AR5 Summary for Policy Makers)

In short, you are looking at a balance sheet of the major types of emissions that have either a warming or cooling effect on climate. Bars that extend to the left of the 0 signify a cooling effect; bars that extend to the right signify warming. The longer the bar, the more warming or cooling a given type of emissions contributes. What becomes immediately obvious is that carbon dioxide (CO2) and methane (CH4) have the biggest warming influence by far. The other well-mixed greenhouse gases — halocarbons, nitrous oxide (N20), chlorofluorocarbons (CFCs), and hydrochlorofluorocarbons (HCFCs) play a much smaller role.

The situation gets messy when you look at the role that short-lived gases and aerosols play. Some gases like carbon monoxide (CO) and the non-methane volatile organic compounds (NMVOC) — such as benzene, ethanol, formaldehyde — contribute to warming, but not much. Others like NOx actually slightly cool the climate overall if you consider how these gases interact with other substances in the atmosphere. Things get even messier if you look at aerosols. Mineral dust, sulfate, nitrate, and organic carbon have a cooling effect. On the other hand, black carbon causes warming. Albedo changes due to land use and changes in solar irradiance are minor in comparison to the other factors.

That’s a lot of variables, but one reason I like this chart is the error bars and the “level of confidence” column. The error bars give you a sense of how much uncertainty there is when it comes to the effects of various emissions. Look at the aerosol section, for instance, and you will see that the error bars are quite large and there is still some uncertainty about how aerosols affect clouds. The level of confidence column offers further clues to what scientists understand well and which areas they are less confident about. VH stands for very high confidence; H stands for high confidence; M stands for medium confidence; and L stands for low confidence.

What is striking is that even when you account for the error bars, there is little doubt that carbon dioxide and methane are warming the climate.


(Image by the NASA Global Climate Change website)

A third graphic, produced by NASA but based on data described here, is particularly compelling. Based on atmospheric information preserved in air bubbles in ancient ice cores, the plot offers a view of carbon dioxide levels in Earth’s atmosphere for the past 400,000 years. As this graph makes obvious, it has been a long time since carbon dioxide levels have been anywhere near where they are now.

For a much more recent view of carbon dioxide levels, the animation above is useful. Produced by NASA’s Scientific Visualization Studio, the video shows a time-series of the distribution and concentration of carbon dioxide in the mid-troposphere, as observed by the Atmospheric Infrared Sounder (AIRS) on the Aqua spacecraft. For comparison, the fluctuations in AIRS data is overlain by a graph of the seasonal variation and interannual increase of carbon dioxide observed at the Mauna Loa observatory in Hawaii. You can clearly see seasonal variations in carbon dioxide levels, but notice also that the mid-tropospheric carbon dioxide shows a steady increase in atmospheric carbon dioxide concentrations over time. That increase is because of human activity.

Image by Harvard University Press.

(Image by Harvard University Press)

My last recommendation will take longer for you to get through, but it is an invaluable resource. Physicist Spencer Weart offers a detailed but understandable account of the history of climate science research in his book The Discovery of Global Warming. You can read an extended version of book online on the American Institute of Physics’ website. If you make it all the way through, you will know far more than most people about the climate.

14 Responses to “Four Graphics (and a Book) that Help Explain Climate Change”

  1. phbaybutt says:

    How can you be sure the way you measure carbon is accurate ? Is it based on your theories ? Are your theories developed to prove that mankind is affecting the climate
    Do you know what “hubris” means ?

    • Cat says:

      No, I believe you’re referring to science, the rigorously challenged, accumulated knowledge of the species. It’s what has prevented you and yours from succumbing to many horrible diseases. It’s what makes your cell phone work. In assuming that the underpinning work hasn’t been confirmed by numerous skeptical scientists hoping to disprove it and thereby make a name for themselves, and that you can imagine personal beliefs have any influence, only serves to demonstrate that you have no idea how it works. This is especially sad in the age of information, where your comment here shows that you have ready access to the means to apprehend this basic and transformative concept.

      • Doc says:

        I believe you mean ‘comprehend’, not ‘apprehend’. It does make a difference…

        • Cat says:

          No actually, I meant exactly what I wrote. Definition 2 in the two dictionaries I just checked (in case I had actually made a mistake) are both “to understand, perceive”. Also to recognize, appreciate.

          • Question mark says:

            Strange how it happens that true and legitimate discussion get side track by human insecurities….. would be curios to hear your best possible theorems you both have to offer, if you can…

    • YLevin says:

      Do you mean measurement of current CO2 concentration in the air, or CO2 emitted by people? The first one is very accurate, and if you doubt the results, hire a lab to do it for you. If you don’t like the result they come up with, hire another one. Soon you’ll be broke, and all their measurements will confirm the current CO2 concentration in the atmosphere. CO2 emitted by people is calculated very accurately (at least for the purpose of our discussion) from knowing how much fuel is used. If you know how many times a year you refuel your car, and you know exactly how much CO2 is released from burning a gallon of fuel, then you know exactly how much CO2 your car releases in a year. The same applies to all users of fuels, such as factories, power plants, etc. In addition, we know very accurately how much CO2 is released by other than man, such as volcanoes, plants, etc. As it turns out, man releases 100 times more than volcanoes (300 million ton compared to 30 billion).

      How can we be sure? because we can (and do) TEST our measurements by physically measuring CO2 emissions and comparing them to the estimates. They match. If you’ve had your car’s emissions tested, you know exactly how much CO2 it releases. Power plants and factories have CO2 sensors on (a representative sample of) their smokestacks.

      Any other questions?

      • Jim Macdonald says:

        How about all the CO2 that is exhaled by all humans and animals on the planet?

        Why is that conveniently ignored?

        • Seriously says:

          if you have a bucket of water and you pump water out and then immediately back in … How much has the amount of water in the bucket changed?

          I trust you see how silly your comment was? Also scientists can test the source of CO2 in the atmosphere isotopically. CO2 from living biomass, volcanism, fossil fuels, etc all have distinc chemical signatures. Guess which we observe today?

    • InTheory says:

      Deniers seem to have a handbook of goofy questions. They also don’t understand that polls and opinions of uneducated parrots are not equivalent to the scientific method. What your neighbor thinks, what Rush Limbaugh thinks is irrelevant to the reality as demonstrated by actual climate scientists. Just because your favorite politician thinks global warming is a hoax perpetrated by China doesn’t make it true, it just proves that he’s reading from the same goofy handbook.

      Here’s one of the best representations of CO2 levels I’ve seen. It covers 800,000 BCE to 2014 and therefore covers a number of glacial and interglacial periods:

  2. James says:

    Even if the numbers are close, no one can prove that is what is making it get warmer. The fact that the sun is getting warmer is rarely mentioned. How they can accurately measure volcanic Co2 activity below the ocean or even above the ocean is complete speculation. Besides, now that the Pacific ocean is full of very bad radiation, we are all SOL anyway.

    • GuruOfChem says:

      Based on your post, I am forced to conclude that you either have NO idea what you are talking about or you are trolling. If you are trolling, disregard the following…

      YES, it has been proven that CO2 traps heat in the lower atmosphere that would otherwise radiate into space, and YES, there is far more C)2 now than there has been in half a million years. YES, ocean levels of CO2 can be accurately measured (and are rising dramatically too), and YES, volcanic emissions are studied not only to help understand warming but also to help understand and forecast eruptions. This is information you can learn if you choose to – if you choose not to, quit posting your ignorance for all to see…

  3. enzo says:

    Quite interesting

  4. Hiro Kawabata says:

    Correlation: 0998

    The plot of ice core CO2 and recently measured CO2.
    Remarkable how exactly the two disparate data sets match up.
    Or was the ice core set allowed to “float” relative to the other to obtain such a perfect match?

  5. Allan Carl says:

    In the days of old I could see how one could be led to believe in the supernatural as well as many other forms of mass hallucination that said you do need to be somewhat judicial in what and where information is found on the internet or anywhere for that matter. These days you need not look at a graphic rather step outside in the region where I live and have a decent memory to know its warmer as well as seeing the changes. It’s my very humble opinion that Americans as a whole are just slightly more retarded for the lack or want to put it in other terms.

    I also know what is common political, social, beliefs in the US and our western influenced cohorts is far less accurate than the truth. Both problems stem from a lack of education, fear and a serious lack of the rule of law for the elites and ruling classes. If you have any doubts to the validity to what I wrote simply open up Noam Chomskys book “Manufacturing Consent” and example after example are given and can be looked up independent of the book.
    If it weren’t for the beauty I see at any turn of the head and an incredible urge to see the human species not just live but to thrive. I would have asked NASA to build me a spacecraft and shoot me out on a brief but scenic veiw of the solar system on my way to interstellar space so I could report back for as long as I could as to the affects of long term space travel on the body. Lol