Open Letter to President-Elect Donald Trump on Global Warming

Honorable President-Elect Trump:

By the end of the present century, 2100, man-made global warming could be a major existential threat to humanity’s way of life on earth, and to the broad ecological balance underpinning our lives and those of future generations.

Everyone will feel the consequences of worsening global warming.  I’m a scientist who is deeply concerned for the welfare not only of our planet’s present inhabitants, but especially for our progeny:  those whom we already know, and those yet to be born.  You and your family, including your children and your several grandchildren, as well as the members of your incoming administration and their families, will be among those who will be impacted as warming continues. 

 Why should we care about global warming?   Here’s a montage of images showing a sampling of damage and harm already brought on by warming, both domestically and abroad:

Extreme events negatively impact our society and our economy.  The examples shown here have been determined to be at least partially due to the effects of global warming.  Clockwise from upper left:  A wildfire in heat- and drought-stricken California threatens a home in 2015 (Source: http://us-news.us/firefighter-dies-in-wind-fueled-northern-california-wildfire); fair weather tidal flooding encroaches on coastal communities in Miami, FL in 2014 (Source: http://www.pbs.org/newshour/bb/south-florida-rising-sea-levels/) and in Norfolk, VA in 2012 (Source: http://www.pbs.org/newshour/bb/politics-july-dec12-norfolk_12-06/); a scientific paper in the Proceedings of the [U.S.] National Academies of Science (2015) showing that the Syrian civil war arose partly from  socioeconomic instability due to a multi-year drought, brought on by global warming, in the years preceding the hostilities (emphases added; Source: www.pnas.org/cgi/doi/10.1073/pnas.1421533112); and heavy flooding in Baton Rouge, LA in 2016, due to extremely intense rainfall (Source: http://www.climatecentral.org/news/louisiana-floods-directly-linked-to-climate-change-20671).

 

The Paris Agreement of December 2015 to limit global greenhouse gas emissions is a landmark accord. The U. S., China and other major emitters of greenhouse gases provided important leadership in reaching agreement.  197 member states of the United Nations signed the accord, and by mid-November 2016 115 nations have ratified it.  It entered into force on November 4, 2016, with U. S. participation.

President-elect Trump, in your interview with the New York Times on Nov. 22, 2016 you stated “I have an open mind to [climate change]. We’re going to look very carefully.”   The nations signing the Paris Agreement look to the U.S. for continued leadership in its implementation, and are apprehensive about the possibility that you will pull the U. S. out of the agreement.

 

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Science provides an objective view by which we see the world.  We humans can’t change the scientific framework underlying the causes of global warming, its worsening, and its harmful effects.  Denying the present egregious climate patterns cannot change them or make them disappear.

Climate scientists understand that excess man-made CO₂ leads to increased warming of the Earth system due to the greenhouse effect.  The relevant facts and scientific data are summarized here:

·        Carbon dioxide (CO₂) is an important atmospheric greenhouse gas (one that traps heat leaving the surface of the earth and returns some of it to the surface.  Other man-made chemicals are also greenhouse gases, but in this letter I focus on CO₂).

·        CO₂ is a main product formed by burning fossil fuels; the excess CO₂ formed when humans use fossil fuels for energy has been accumulating in the atmosphere since the industrial revolution began.

·        Physical scientists recognized the greenhouse activity of CO₂ as early as the nineteenth century, and understood even then that continued burning of fossil fuels could lead to warming of the earth. 

·        A particular property of CO₂ (carbon isotope ratios) measured over time shows categorically and irrefutably that the increasing amount of CO₂ in the atmosphere originates from humans’ use of fossil fuels, and not from any other possible source.

·        For the last 800,000 years atmospheric CO₂ has never exceeded 280 volumes per million volumes of air (parts per million, ppm).  Humanity’s burning of fossil fuels has now pushed that above 400 ppm (www. CO₂.earth).  The rate that we are adding new CO₂ is far faster than at any time in the last 800,000 years.

·        Most CO₂ we add to the air stays in the atmosphere for centuries or longer.  So the coal burned in the nineteenth century produced CO₂ that’s still in the air today.  This is why man-made CO₂ is such a problem.

·        Because of the greenhouse activity of CO₂ the earth’s temperature has been increasing, following the same long-term trend as the increase in CO₂.

·        Climate models show that the recent increase in global average temperature is due to the increasing excess man-made CO₂ in the air, not simply to natural physical processes of the earth system.

·        Annual global average surface temperatures in 2014 and 2015 reached record highs never seen in the historical record (beginning 1880).  This record-setting trend continues through August 2016.

Historical global warming up to the present has already caused major damage and visited significant harms on humans the world over.  President-elect Trump, the extreme events presented in the graphic montage above are just a small, unrepresentative set of examples of damaging, destructive and or disruptive events already brought on by global warming.  The damages and disruptions brought by these events require significant fiscal outlays at the local, state and federal levels to repair damage and to construct adaptive infrastructure in the hope of averting future damage.  These expenses have been unforeseen and so not included in budgets.  Ultimately they are borne by our taxpayers.  In addition, insurance companies will need to include new, and higher, risk premiums due from insured clients to account for the increased likelihood of future claims.  These expenses, consequences of burning fossil fuels, are not built into the sales price of the fuels, which reflect only the costs of extraction, processing and distribution of the fuels. 

President-elect Trump, the demand for fossil fuels and resulting further global warming will only increase in future decades unless we intervene.  The rapidly increasing global population clearly adds to energy demand.  As developing countries grow economically they demand more energy to sustain their progress. 

If future energy demand is fulfilled using fossil fuels models project that the resulting global warming will cause more intense heat waves, intensified drought, crop failures and forest wildfires in certain regions of the world; more extreme precipitation and resulting severe flooding in other regions; and continued sea level rise with worsening coastal flooding.  Thus harms and damages already experienced will grow more severe. 

·        Climate models successfully reproduce past historical climate trends.  This provides confidence that they can illustrate future developments.

·        These models show that future excess global warming depends in almost a straight-line fashion on the excess addition of CO₂ to the earth’s atmosphere.  Limiting CO₂ emissions will minimize the future temperature increase.

·        In the absence of measures adopted worldwide to constrain further CO₂ emissions by 2100 the global average temperature could reach about 8.5ºF (4.7ºC) above the average temperature during the interval 1861-1880.  Presently that average has already increased by about 1.6ºF (0.9ºC).

·        The kinds of harms and damages already identified would become much worse in the absence of emission constraints.

·        Rising sea levels are already irreversible because, averaged over a full year, the temperatures in polar regions, and over mountain glaciers, are warm enough to yield net melting of ice.  Also, as water warms, it expands, further contributing to rising seas.

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President-elect Trump, the Paris Agreement affords your administration the opportunity to expand investment in renewable energy, creating large numbers of new jobs.  In the coming decades it has been estimated that US$20 trillion will be needed to provide expanded global energy demand. Your administration should enthusiastically embrace the Agreement, using it as an incentive to promote profitable new investments in renewable energy that will expand employment among America’s workers.

© 2016 Henry Auer

Attribution of Extreme Events to Global Warming

The public, when contemplating global warming, includes those who question whether warming underlies the occurrence of extreme weather and climate events.  The U.S. National Academies of Science, Engineering and Medicine recently issued a report, “Attribution of Extreme Weather Events in the Context of Climate Change”.  It emphasizes that the appropriate format for questions concerning this issue can be phrased in terms such as “Are events of this severity becoming more or less likely because of climate change?” 

The report emphasizes that because of rapid advances in data analysis and climate modeling the severity of many extreme events can be attributed to contributing factors arising from warming.  It includes a schematic image, shown here, characterizing how the increasing degree of understanding of various types of events leads to increasing confidence in the degree to which we can attribute severity to contributions from global warming.

This post concludes with a selection of examples from the climate literature where such analyses have been made, leading to affirmative statements of attribution such as considered here.

Recently weather news has reported on extreme events in many regions of the world. 

• The American states of Texas and Louisiana, and their neighbors, had intense rain for over a week in early 2016, triggering record-breaking flooding in the area.    

• The American West has suffered severe drought conditions for four years, straining water supplies and lowering yields of important crops. 

• Over the past winter England and Wales have had prolonged bouts of heavy rain and flooding, including hundreds of flood alerts and warnings, more than 30 of which were labeled severe.  

• Perth, Australia had a heat wave four days long with temperatures over 40ºC (104ºF) in February 2016, and has had seven days over this temperature this season.  

• Pakistan has had increasing numbers of serious flooding events over the last century, including 40 events in the last 15 years.  Most of these are accompanied by loss of life and social dislocation, and significant damage to structures and agricultural lands.

These few anecdotes are potentially significant indicators of the effect that global warming is having at regional and local levels around the world.  Indeed, increased rates of occurrence of such phenomena are predicted with high confidence in recent global warming reports.  But in discussing the role of warming at the scale of such geographically small areas it is important to evaluate whether each one in fact is related to warming.  For example, if few or none are, climate science would be hard pressed to persuade policymakers and the public to undertake efforts to minimize further warming and adapt to its effects.  On the other hand, if it can be shown that there is indeed a contribution from warming, then climate science is justified in actively pursuing appropriate policies such as those agreed to at the United Nations conference in Paris in December 2015.

Here we discuss the question of whether, and how, extreme events can be attributed to global warming.

The U. S. National Academies of Sciences, Engineering, and Medicine issued the report “Attribution of Extreme Weather Events in the Context of Climate Change” (2016); Washington, DC: The National Academies Press (the Report) on March 10, 2016.  The Report emphasizes that extreme events, just as all our weather every day, results from the interactions of many atmospheric forces and processes.  For this reason, it makes the very important point that we can not justifiably ask a question such as “Was this extreme event caused by [man-made] climate change, yes or no?”  Such a simplified black-or-white question overlooks the complexity in climate and weather. 

Rather the Report offers different questions phrased as “Are events of this severity becoming more or less likely because of climate change?”; or, for single events such as local storms, the question could be “To what extent was the storm intensified, or its precipitation increased, because of climate change?”  Note that the questions deemed appropriate seek expressions of likelihood, rather than the certainty demanded by the yes-or-no question.  To any viewer of a televised weather forecast this should hardly be surprising.  After all, these daily predictions always provide likelihoods for sunshine (clear, partly cloudy, mostly cloudy, etc.) as well as percent probabilities of rain, sleet or snow.  In the same way, and for the same reasons, the Report concludes that statements of attribution should be phrased in terms of the probability or likelihood that global warming was a climatic factor contributing to the occurrence of the extreme event.

The Report summarizes its detailed deliberations about attribution of events to known or understandable contributing factors with a simplified conceptual diagram, shown here

 

Schematic diagram showing how our confidence (vertical axis) in attributing different kinds of extreme events to man-made climate change depends on our understanding of the extent to which climate change affects the particular type of event (horizontal axis).  Different types of extreme events are shown by the differently colored labeled circles.  The dashed line represents where a particular type of extreme event would fall if we had an ideal ability to attribute how climate change affects it.  In reality all the circles fall below the dashed line because our ability to attribute the specific events to man-made climate change is less than perfect.  Note that the understanding/attribution level is high for temperature events (upper right), and that these become lower as we pass through extreme rainfall (near the center) to severe convective storms (e.g., thunderstorms and tornadoes; lower left).

Source: U. S. National Academies of Sciences, Engineering, and Medicine,  “Attribution of Extreme Weather Events in the Context of Climate Change” (2016); Washington, DC: The National Academies Press. doi: 10.17226/21852.

 

 

The Report identifies two ways to label an event as “extreme”.  We have to be able to distinguish a supposed extreme event, potentially caused in part by the effects of global warming, from normal behavior.  First, data characterizing the event could be shown to differ from comparable data for a reference period extending over a sufficiently long period of time, with a high level of statistical significance.  Alternatively, data characterizing the event could be successfully modeled in a climate model that includes man-made global warming factors, whereas it could not be modeled by a similar model run excluding those factors, again, with a high level of statistical significance.  An event that fulfils either of these conditions can then be labeled as an event to which global warming contributes to its extreme character.
 

Extreme events had already been attributed to global warming before this Report. 

 

• Analysis of data over the 49 year period from 1951-1999 shows that global warming is responsible for extremes of rainfall over the Northern Hemisphere.  Min and coworkers (Nature, 2011, Vol. 470, pp. 378-381, doi:10.1038/nature09763) showed that “human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of … Northern Hemisphere land areas.”  This work is significant because it covers a period of time in which greenhouse gas levels, and global average temperatures, were much lower than at present.

 

• Extreme rainfall and catastrophic flooding in England and Wales in 2000 was very likely due to human-induced global warming.  Pall and coworkers carried out a probabilistic analysis of weather patterns and likelihood of flooding in the region (Nature, 2011, Vol. 470, pp. 382-385, doi:10.1038/nature09762). During October and November 2000 England and Wales had the heaviest rainfall since records began in 1766, leading to severe flooding. The authors concluded “it is very likely that global [human-induced] greenhouse gas emissions [occurring during the twentieth century] substantially increased the risk of flood occurrence…in autumn 2000.”

 

• Kelley and coworkers (Proc. Natl Acad. Sci., published online before print March 2, 2015) report on the worst drought in recorded history in Syria and neighboring countries just prior to the “Arab Spring”.  The drought was serious enough that large numbers of farmers left their villages and migrated to Syria’s cities.  This caused major social and political turmoil and is considered to be a contributing factor to Syria’s ongoing civil war.  The authors found that human-derived greenhouse gases contributed to the drought.

 

• Moore and Lobell (Proc. Natl. Acad. Sci., vol. 112 no. 9, pp. 2670–2675, 2015) analyzed changes in crop yields and climate change across Europe between 1989 and 2009.  Large scale decreases in yields were found in many localized regions, which correlated with increased temperatures and decreased precipitation over the 20 year period studied.

 

• Diffenbaugh and coworkers (Proc. Natl. Acad. Sci., published online before print March 2, 2015) examined the drought in California from December 2012 to September 2014, likely the worst in 1000 years.  By simulating the region’s climate in model calculations the authors found that the extra amount of greenhouse gases added by human activity likely resulted in higher temperatures and reduced precipitation in the region.  This factor also contributes to a high risk of continued severe droughts.

 

• Williams and coworkers also conducted detailed analyses of climate-related data for California, from 1901 to 2014 (Geophys. Res. Let. 2015; DOI: 10.1002/2015GL064924).  From rigorous statistical analysis the authors estimated that global warming was responsible for 8-27% of the observed excess drought conditions for 2012-2014, and for 5-18% for 2014 alone.  These findings indicate that although drought conditions may originate from various climatic factors operating cyclically over many years, its full extreme extent in the current drought has been worsened by global warming, producing the current record conditions.

 

• Cook and coworkers (Sci. Adv. 1, e1400082 (2015); published electronically 12 February 2015) assessed drought conditions in the American Southwest and Central Plains.  Assuming that unrestrained emission of greenhouse gases would continue, the risk of severe droughts in these regions is projected to be extremely high, by various measures between about 69% and 97% in the second half of this century.

 

Conclusion

 

The Report by the National Academies makes clear that climate science has advanced remarkably in the last decade, so that attributions of global warming as a contributing factor to extreme events can reliably be made after appropriate analysis.  This depends on use of one or both of the methods, either data based or model based, mentioned above.  The progress making this possible includes the availability of far more observational data, on the one hand, and constant improvements in climate models on the other.  As a result statements of attribution, when merited based on analysis, now authoritatively support the role of man-made global warming, due to humanity’s continued and increasing use of fossil fuels, in the increasing severity of various types of extreme climate and weather events.  We all, as citizens of countries around the world, must marshal our efforts to reduce emissions as aggressively as possible.  The goal should be achieving near zero annual emission rates within a few decades, say by mid-century.

 

© 2016 Henry Auer

Record Greenhouse Gases Continue to Accumulate in the Atmosphere

We experience weather at the local or regional level.  Here, one person may be in a heavy rainstorm, while there, somewhere else in the world, another could be in an uncomfortable heat wave.  Daily or weekly weather, however, is not the same as long-term regional or global climate; climate relates to yearly, multi-year, and even decade-long behavior. 

The world’s climate is affected by the atmospheric accumulation of greenhouse gases (GHGs), which continued unabated during 2013.  GHGs in the atmosphere preferentially retain heat radiating from the earth’s surface and prevent its escape to space. 

Record High Levels of Carbon Dioxide.  The World Meteorological Organization (WMO), an agency of the United Nations, reported recently that the global average concentration of carbon dioxide (CO₂), a major GHG, reached a record level of 396 parts per million (ppm; volume of CO₂ gas in 1 million volumes of air) in 2013 (see the graphic below). 

 

 

Atmospheric concentration of CO₂ in ppm, reported monthly from 1984 to the present.

Source: WMO; https://www.wmo.int/pages/mediacentre/press_releases/pr_1002_en.html

 

The WMO evaluates observations gathered from many land-based stations, ship-based observatories and aircraft.  The increase in CO₂ from 2012, 2.9 ppm, was the largest yearly change since 1984.  The present CO₂ concentration is 42% higher than that before the industrial revolution began during the century between 1750 and 1850.  The dramatic increase in CO₂ emissions in the last 160 years, coinciding with the increasing role that fossil fuels have played in powering the world’s economic growth during that period, is shown below.



Annual rates of emission of CO₂ (evaluated on the basis of the carbon portion of the carbon dioxide molecule) from the three main fossil fuels, plus the production of cement from limestone.  The amounts shown represent about 80% of all human-derived carbon, with most of the remainder arising from human-induced deforestation.

Source: The Third U. S. National Climate Assessment (data from Boden et al. 2012); www.nca2014.globalchange.gov

 

Even more recently the New York Times reported that another international group of climate scientists likewise found that GHG emissions in 2013 reached record levels.  Worldwide this group found that the increase from the previous year was 2.3%, while in the U. S. the increase was 2.9%, opposing a decreasing trend in earlier years.

Why should we care about this pattern in CO₂ levels?

As atmospheric CO₂ levels trend higher the long-term worldwide average temperature of the earth’s atmosphere has also been increasing, in concert with the increasing concentration of CO₂ (see the graphic below).  This has been happening because of the greenhouse effect of CO₂ and other greenhouse gases (also reported by the WMO).

Correlation between global temperature and atmospheric CO₂ concentration from 1880 to 2012.  The thick black line gives the yearly CO₂ concentration in parts per million (volumes of CO₂ present in 1 million volumes of air) with values along the right vertical axis.  The ends of the blue and red lines show the temperature with values along the left vertical axis.  The horizontal line shows the average temperature across this time span.  The ends of the blue lines show the temperature values for years in which the temperature was below the average, and the ends of the red lines show the temperature values for years in which the temperature was above the average.

Source: The Third U. S. National Climate Assessment; www.nca2014.globalchange.gov.

 

The global average temperature has increased by about 0.7-0.8ºC (1.3-1.4ºF) over pre-industrial temperatures.  As a current example, U. S. government scientists report that each of the months June, July and August 2014 were the hottest on record, when averaged over the entire globe.  These temperatures exceeded the previous monthly records set in 1998. 

The increased CO2 levels arise directly as a result of humanity’s burning of fossil fuels for energy, and not from natural causes (see also the U. S. National Climate Assessment (a U. S. government interagency report) issued May 2014).

There have been many reports over the past several months documenting increasing GHG emissions and warmer long-term global average temperatures.  These include the Fifth Assessment Report of the United Nations-sponsored Intergovernmental Panel on Climate Change, the Third U. S. National Climate Assessment, and the two reports mentioned here.  The persistent drumbeat of reports on global warming emphasize the conclusion that the increase in atmospheric CO₂ and the resulting increase in global average temperature are manmade: they originate from humanity’s burning of fossil fuels for energy to drive economic development. 

Higher worldwide temperatures are leading to more, and more extreme, climate and weather events.  For example, warmer temperatures permit the atmosphere to hold more water vapor, so that many regions will likely experience heavier rain and snow, leading to flooding.  In other areas, higher temperatures will likely increase evaporation of moisture from the land leading to drought.  Both flooding and drought can reduce crop yields, leading to higher prices or famine.  Sea levels are rising as land-based ice sheets and glaciers melt, with the runoff entering the ocean.  All these trends lead to physical and socioeconomic harm to humanity as extreme patterns and catastrophes inflict more damage than in earlier times.

Human health is likewise significantly harmed, as air quality is degraded and as warmer conditions make it easier for disease-bearing microorganisms to flourish and infect the population.

Increased emission of GHGs is a worldwide problem requiring a worldwide solution.  The international community is currently beginning final negotiations on a worldwide treaty to reduce GHG emissions, undertake adaptation measures and assist those nations most adversely affected by global warming.  The participating nations must approach these negotiations in good faith, with an eye to the future, so they can agree to meaningful abatement and adaptation policies.  Our wellbeing, and that of future generations to follow, demands no less.

© 2014 Henry Auer