Tuesday, July 16, 2019

Warmest June on Record Globally

Data released Monday by NASA shows that June was the warmest on record globally (see this Washington Post article).

The time series of Junes during the instrumented record (i.e., back to 1880) is shown below.  One can see the long-term warming trend, as well as the year-to-year variability caused by many factors including the El Niño/Southern Oscillation (ENSO), volcanic eruptions, and other climate-system variations.

I've also added some news items and personal notes to provide some context as to what has been going on over the past five decades.

In 1967, I was born.  Just two years later, and 50 years ago on July 20, 1969, humans walked on the moon in what was a truly audacious human accomplishment.  Although I have no memory of the Apollo program, NASA's space program had a real impact on my interest in science.  I remember, for example, requesting and receiving photographs of the Space Shuttle as a teenager.

In 1975, Wally Broecker published a paper in science entitled Climate Change: Are We on the Brink of a Pronounced Global Warming. In that paper, he wrote,
"A strong case can be made that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide.  By analogy with similar events in the past, the natural climatic cooling which, since 1940, has more than compensated for the carbon dioxide effect, will soon bottom out.  Once this happens, the exponential rise in the atmospheric carbon dioxide content will tend to become a significant factor and by early in the next century will have driven the mean planetary temperature beyond the limits experienced during the last 1000 years."
In 1979, the National Academy of Sciences published a report entitled Carbon dioxide and Climate: A Scientific Assessment.  The report is sometimes referred to as the Charney Report since Jule Charney, a giant in meteorology from the mid 20th century until his death in 1981, served as chairperson for the group preparing the report.  That report concluded,
"When it is assumed that the CO2 content of the atmosphere is doubled and statistical thermal equilibrium is achieved, the more realistic of the modeling efforts predict a global surface warming of between 2˚C and 3.5˚C, with greater increases at higher latitudes."
In 1985, I graduated from high school.  Global warming is not something that I recall being aware of.  I began to study meteorology because I was interested in weather forecasting.  However, in my junior year, I took a physical meteorology course taught by Craig Bohren.  In that class, we developed simple analytical models of the planetary energy balance to better understand the theoretical underpinnings of processes that cause the planet to warm or cool.

At the time, as I recall, there was vigorous debate about whether or not we could detect a human influence on climate.  In 1988, Jim Hansen testified in congress about global warming, arguing that the signal of human-caused global warming was now detectable.  A good perspective on this testimony based on current knowledge is available below.

The role of both natural and human caused climate change in recent warming is something I can remember being debated at times in graduate school.   There were a few reasons for this.  First, we were still in the early stages of global warming.  Second, teasing out the warming signal from imperfect observations remained challenging.  And third, our computer models remained relatively rudimentary.  

From 1997-1998, the strongest El Niño on record occurred, pushing global temperatures to what were then remarkable levels (I've labeled this the 1997-1998 Super El Nino above).  Subsequently, temperatures from this period were often used for the start of trend calculations to argue that global warming had stopped or flattened.  

In 2007, I was asked to lead a report on climate change for Governor Jon Huntsman Jr's Blue Ribbon Advisory Council on Climate Change (available here).  Several other Utah scientists contributed.  By this time, the nail was in the coffin concerning whether or not the planet was warming and the evidence for human-caused climate change quite strong.  In that report, we concluded that there was no longer any scientific doubt that the planet was warming and that changes in ice cover, snow cover, and sea level were consistent with this warming.  We also concluded that there was very high confidence that human-generated increases in greenhouse gas concentrations were responsible for most of the global warming during the prior 50 years and that ongoing greenhouse gas emissions at or above current levels will produce global temperature, sea level, and snow and ice changes greater than those observed in the 20th century.

A look a the June temperature record above, as well as what is happening around the planet in recent years, shows that things are playing out largely as anticipated, so it's no surprise to me that we see predominantly high temperature records being set, continued declines in arctic ice, continued declines in glacier ice, and accelerating sea level rise.  

If you don't think this is happening, I'm sorry, but you are wrong.  This is a done deal.  We are already living in a climate that is different than the one that existed in the 20th century and bigger change is coming.  Temperature change is often emphasized, but it is water that will deliver the most severe climate impacts for humans through sea level rise, more persistent drought, more intense rainfall, and other changes to the water cycle (e.g., more precipitation falling as rain instead of snow).

When I was in Innsbruck, I found an exhibition in one of the museums on smoking.  

Someday, articles like the one below will similarly displayed in a museum.  People will look at have the same response that I did about the commercial above.  

"What the hell were they thinking?"


  1. Jim, I've noticed that the northern hemisphere jet stream shown on the U of Maine Climate Reanalyzer site has been mostly scattered and disorganized for months, while the southern hemisphere jet stream looks pretty normal. Do you have an explanation for this?

  2. Thanks for the graph, it's absolutely crazy that the super el nino of 98 was just over 20 years ago, yet is now pretty much average. It was such a big deal back then. The timeline of these changes is seriously scary.

  3. Looks like we might be in for a heat wave to start next week. Current NWS forecast for KSLC shows a high of 102 Monday and 103 Tuesday. Record for both days is 104.
    They even mentioned the possibility of a heat advisory for northern Utah in their latest discussion. Can't remember the last time we had one of those.