Global & Disaster Medicine

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2017 Was the Second Hottest Year on Record

2017 Was the Second Hottest Year on Record

acquired January 1 – December 31, 2017 download large image (634 KB, PNG, 1613×859)

Earth’s global surface temperatures in 2017 ranked as the second warmest since 1880, according to an analysis by scientists at NASA’s Goddard Institute for Space Studies (GISS). Continuing the planet’s long-term warming trend, globally averaged temperatures in 2017 were 0.90 degrees Celsius (1.62 degrees Fahrenheit) warmer than the 1951 to 1980 mean. That is second only to global temperatures in 2016.

In a separate, independent analysis, scientists at the National Oceanic and Atmospheric Administration (NOAA) concluded that 2017 was the third-warmest year in their record. The minor difference in rankings is due to slightly different methods used by the two agencies to analyze global temperatures. The long-term records of the two agencies remain in strong agreement, and both analyses show that the five warmest years on record have all taken place since 2010.

The map above depicts global temperature anomalies in 2017, according to the NASA GISS team. The map does not show absolute temperatures; instead, it shows how much warmer or cooler each region of Earth was compared to a baseline average from 1951 to 1980.

Because the locations and measurement practices of weather stations change over time, there are uncertainties in the interpretation of specific year-to-year global mean temperature differences. Taking this into account, NASA estimates that the 2017 global mean change is accurate to within 0.1 degree Fahrenheit, with a 95 percent certainty level.

acquired January 1 – December 31, 2017 download large image (23 MB, GIF, 2048×1127)

“Despite colder than average weather in any one part of the world,” said GISS Director Gavin Schmidt, “temperatures over the planet as a whole continue the rapid warming trend we have seen over the last 40 years.”

The animated figure above shows global temperature anomalies for every month since 1880, a result of the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) model run by NASA’s Global Modeling and Assimilation Office. Each line shows how much the global monthly temperature was above or below the annual global mean from 1980–2015. The column on the right lists each year when a new global record was set.

Earth’s average surface temperature has risen a little more than 1 degree Celsius (about 2 degrees Fahrenheit) during the past century or so, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere. 2017 was the third consecutive year in which global temperatures were more than 1 degree Celsius (1.8 degrees Fahrenheit) above late 19th-century levels.

Phenomena such as El Niño and La Niña—which warm and cool the tropical Pacific Ocean and cause corresponding variations in global wind and weather patterns—contribute to short-term variations in global temperatures. Also, weather dynamics affect regional temperatures, so not every region on Earth experienced similar amounts of warming last year. Warming trends are strongest in the Arctic regions.

The NASA GISS team assembles its analysis from publicly available data acquired by roughly 6,300 meteorological stations around the world; from ship- and buoy-based instruments measuring sea surface temperature; and from Antarctic research stations. This raw data is analyzed using methods that account for the distribution of temperature stations around the globe and for urban heating effects that could skew the calculations. (For more explanation of how the analysis works, read World of Change: Global Temperatures.)

Analyses from the United Kingdom Met Office and the World Meteorological Organization also ranked 2017 among the top three warmest years on record. Scientists from NOAA, WHO, and the UK Met Office use much of the same raw temperature data, but with different baseline periods or slightly different methods to analyze Earth’s polar regions and global temperatures.

NASA Earth Observatory images by Joshua Stevens, based on data from the NASA Goddard Institute for Space Studies. Caption by Kate Ramsayer, NASA Goddard Space Flight Center, with Mike Carlowicz.

In situ Measurement

Jakarta is sinking faster than any other big city on the planet, faster, even, than climate change is causing the sea to rise — so surreally fast that rivers sometimes flow upstream, ordinary rains regularly swamp neighborhoods and buildings slowly disappear underground, swallowed by the earth.

NY Times

  • Jakartans are digging illegal wells, drip by drip draining the underground aquifers on which the city rests — like deflating a giant cushion underneath it.
  • About 40 percent of Jakarta now lies below sea level.



Global Temperatures Over the Decades

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The world is getting warmer. Whether the cause is human activity or natural variability—and the preponderance of evidence says it’s humans—thermometer readings all around the world have risen steadily since the beginning of the Industrial Revolution. (Click on bullets above to step through the decades.)

According to an ongoing temperature analysis conducted by scientists at NASA’s Goddard Institute for Space Studies (GISS), the average global temperature on Earth has increased by about 0.8° Celsius (1.4° Fahrenheit) since 1880. Two-thirds of the warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade.

But why should we care about one degree of warming? After all, the temperature fluctuates by many degrees every day where we live.

The global temperature record represents an average over the entire surface of the planet. The temperatures we experience locally and in short periods can fluctuate significantly due to predictable cyclical events (night and day, summer and winter) and hard-to-predict wind and precipitation patterns. But the global temperature mainly depends on how much energy the planet receives from the Sun and how much it radiates back into space—quantities that change very little. The amount of energy radiated by the Earth depends significantly on the chemical composition of the atmosphere, particularly the amount of heat-trapping greenhouse gases.

A one-degree global change is significant because it takes a vast amount of heat to warm all the oceans, atmosphere, and land by that much. In the past, a one- to two-degree drop was all it took to plunge the Earth into the Little Ice Age. A five-degree drop was enough to bury a large part of North America under a towering mass of ice 20,000 years ago.

The maps above show temperature anomalies, or changes, not absolute temperature. They depict how much various regions of the world have warmed or cooled when compared with a base period of 1951-1980. (The global mean surface air temperature for that period was estimated to be 14°C (57°F), with an uncertainty of several tenths of a degree.) In other words, the maps show how much warmer or colder a region is compared to the norm for that region from 1951-1980.

Global temperature records start around 1880 because observations did not sufficiently cover enough of the planet prior to that time. The period of 1951-1980 was chosen largely because the U.S. National Weather Service uses a three-decade period to define “normal” or average temperature. The GISS temperature analysis effort began around 1980, so the most recent 30 years was 1951-1980. It is also a period when many of today’s adults grew up, so it is a common reference that many people can remember.

The line plot below shows yearly temperature anomalies from 1880 to 2014 as recorded by NASA, NOAA, the Japan Meteorological Agency, and the Met Office Hadley Centre (United Kingdom). Though there are minor variations from year to year, all four records show peaks and valleys in sync with each other. All show rapid warming in the past few decades, and all show the last decade as the warmest.

Annual Temperature Anomoly

To conduct its analysis, GISS uses publicly available data from 6,300 meteorological stations around the world; ship- and buoy-based observations of sea surface temperature; and Antarctic research station measurements. These three data sets are loaded into a computer analysis program—available for public download from the GISS web site—that calculates trends in temperature anomalies relative to the average temperature for the same month during 1951-1980.

The objective, according to GISS scientists, is to provide an estimate of temperature change that could be compared with predictions of global climate change in response to atmospheric carbon dioxide, aerosols, and changes in solar activity.

As the maps show, global warming doesn’t mean temperatures rose everywhere at every time by one degree. Temperatures in a given year or decade might rise 5 degrees in one region and drop 2 degrees in another. Exceptionally cold winters in one region might be followed by exceptionally warm summers. Or a cold winter in one area might be balanced by an extremely warm winter in another part of the globe.

Generally, warming is greater over land than over the oceans because water is slower to absorb and release heat (thermal inertia). Warming may also differ substantially within specific land masses and ocean basins. The graph below shows the long-term temperature trends in relation to El Niño or La Niña events, which can skew temperatures warmer or colder in any one year. Orange bars represent global temperature anomalies in El Niño years, with the red line showing the longer trend. Blue bars depict La Niña years, with a blue line showing the trend. Neutral years are shown in gray, and the black line shows the overall temperature trend since 1950.

Annual Temperature vs Average

Since the year 2000, land temperature changes are 50 percent greater in the United States than ocean temperature changes; two to three times greater in Eurasia; and three to four times greater in the Arctic and the Antarctic Peninsula. Warming of the ocean surface has been largest over the Arctic Ocean, second largest over the Indian and Western Pacific Oceans, and third largest over most of the Atlantic Ocean.

In the global maps at the top of this page, the years from 1885 to 1945 tend to appear cooler (more blues than reds), growing less cool as we move toward the 1950s. Decades within the base period do not appear particularly warm or cold because they are the standard against which all decades are measured. The leveling off between the 1940s and 1970s may be explained by natural variability and possibly by cooling effects of aerosols generated by the rapid economic growth after World War II.

Fossil fuel use also increased in the post-War era (5 percent per year), boosting greenhouse gases. But aerosol cooling is more immediate, while greenhouse gases accumulate slowly and take much longer to leave the atmosphere. The strong warming trend of the past three decades likely reflects a shift from comparable aerosol and greenhouse gas effects to a predominance of greenhouse gases, as aerosols were curbed by pollution controls, according to GISS director Jim Hansen.

  1. References

  2. Hansen, J., R. Ruedy, M. Sato, and K. Lo (2010). Global surface temperature change. Reviews of Geophysics, 48 (RG4004)
  3. National Academy of Sciences (2010). Advancing the Science of Climate Change. Accessed December 1, 2010.
  4. NASA (2010, January 21). 2009: Second Warmest Year on Record; End of Warmest Decade. Accessed November 30, 2010.
  5. NASA (2010, January 21). NASA Climatologist Gavin Schmidt Discusses the Surface Temperature Record. Accessed November 30, 2010.
  6. NASA Earth Observatory (2010, June 3) Fact Sheet: Global Warming. November 30, 2010.
  7. NASA Goddard Institute for Space Studies (n.d.). GISS Surface Temperature Analysis. Accessed November 30, 2010.
  8. NOAA National Climatic Data Center (n.d.). Global Warming Frequently Asked Questions. Accessed December 1, 2010.
  9. NOAA Paleoclimatology. (n.d.) Climate Timeline Tool: Climate Resources for 1000 Years. Accessed December 1, 2010.


Researchers around the world analyzed 27 extreme weather events from 2016 and found that human-caused climate change was a “significant driver” for 21 of them.

NY Times

Global Maps

NASA satellites give us a global view of what’s happening on our planet. To explore how key parts of Earth’s climate system change from month to month, click on one of the maps below.

A report from 13 U.S. federal agencies that called evidence of a global, long-term warming trend “unambiguous.”

Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 12-34, doi: 10.7930/J0DJ5CTG.

NY Times

Full Report:


Global Drought

Drought Recovery Taking Longer

As global temperatures continue to rise, the prevailing wisdom in the climate science community is that droughts will grow more frequent and more extreme in the 21st century. Though temperatures were already rising in the 20th century, the global trend in drought length and severity was ambiguous, with no clear pattern. However, the impacts of droughts was less ambiguous, particularly in recent decades.

In a study published in August 2017 in the journal Nature, researchers from 17 institutions found that more of Earth’s land surface is now being affected by drought and ecosystems are taking longer to recover from dry spells. Recovery is particularly worse in the tropics and at high latitudes, two areas that are already pretty vulnerable to global change.

The map above is based on data from that study, which was led by Christopher Schwalm of Woods Hole Research Center. It depicts the average length of time that it took for vegetation to recover from droughts that occurred between 2000 and 2010. The darkest colors mark the areas with the longest drought recovery time. Land areas colored light gray were covered by ice or sand (deserts).

Up until now, most assessments of drought and recovery have focused on the hydrology; that is, has new rain and snowfall made up for the deficit of water in rivers, lakes, and soils? In this new study, researchers focused on the health and resilience of the trees and other plants because full reservoirs and streams do not necessarily mean that vegetation has recovered.

The research team combined observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, ground measurements, and computer models to assess changes in drought. In particular, they measured changes in gross primary productivity, or how well plants are consuming and storing carbon dioxide through photosynthesis. As the analysis showed, plants in many regions are taking longer to recover from drought, often because weather is more extreme (usually hotter) than in the past.

If the time between droughts grows shorter (as predicted) and the time to recover from them keeps growing longer, some ecosystems could reach a tipping point and change permanently. This could affect how much carbon dioxide is stored on land in trees and other vegetation (the land “carbon sink”). If less carbon is being captured and stored, then more of what humans produce would remain in the atmosphere, creating a feedback loop that amplifies the warming that leads to more drought.

“The most important implication of our study,” said Schwalm, “is that under business-as-usual emissions of greenhouse gases, the time between drought events will likely become shorter than the time needed for recovery.”

“Using the vantage point of space, we can see all of Earth’s forests and other ecosystems getting hit repeatedly and increasingly by droughts,” added co-author Josh Fisher of NASA’s Jet Propulsion Laboratory. “Some of these ecosystems recover, but, with increasing frequency, others do not.”

NASA Earth Observatory image by Jesse Allen, using data provided by Christopher Schwalm (WHRC). Story by Michael Carlowicz, with reporting from JPL and WHRC.

The Cost of Hurricanes

NY Times

Why Hurricanes Keep Getting Costlier

“….In 2016, the Congressional Budget Office estimated that hurricanes currently cause about $28 billion, on average, in annual damage nationwide. But those costs are projected to rise 40 percent between now and 2075, after adjusting for inflation.

Nearly half of that projected increase, the C.B.O. said, is because global warming and sea-level rise are expected to make hurricanes and storm surges more severe…..

But half of the expected rise in hurricane costs is the result of expected increases in coastal development. Today, according to the C.B.O., roughly 1.2 million Americans live in coastal areas at risk of “substantial damage” from hurricanes — defined as damage of at least 5 percent of average income. By 2075, that number is forecast to rise to 10 million.


Population growth can also increase hurricane risks by adding newcomers who are unfamiliar with big storms or by clogging roads during evacuations…..”

“…..sea levels along Miami’s coasts have risen 3.3 inches since then [1992], and the city is already seeing an increase in “sunny-day flooding” during high tides. With sea levels higher, a hurricane that struck in a vulnerable place could conceivably produce far greater flooding….. “

Europe: Heatwave “Lucifer”

NASA: Sometime between July 10 and July 12, an iceberg about the size of Delaware split off from Antarctica’s Larsen C ice shelf.

Antarctic Ice Shelf Sheds Massive Iceberg

Sometime between July 10 and July 12, an iceberg about the size of Delaware split off from Antarctica’s Larsen C ice shelf. Now that nearly 5,800 square kilometers (2,200 square miles) of ice has broken away, the Larsen C shelf area has shrunk by approximately 10 percent.

Scientists have been tracking the stability of this ice shelf for several years. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured an image (above) of the new iceberg on July 12, 2017. The false-color view uses MODIS band 31, which measures infrared signals known as “brightness temperature.” This measurement is useful for distinguishing the relative warmth or coolness of a landscape. Dark blue depicts where the surface is the warmest—most notably between the new iceberg and the ice shelf, but also in areas of open ocean or where water is topped by thin sea ice. Lighter blue colors show intact or thicker ice (cooler surfaces).

acquired July 12, 2017 download large image (462 KB, JPEG, 1076×1004)
acquired July 12, 2017 download GeoTIFF file (1 MB, TIFF, 1076×1004)

The calving event was confirmed by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite. The day-night band (DNB) of VIIRS captured this image on July 12, 2017.

The final rupture was first reported by Project MIDAS, an Antarctic research project based in the United Kingdom. Adrian Luckman of Swansea University and MIDAS explains the significance of the calving event in a post here.

Larsen C, a floating platform of glacial ice on the east side of the Antarctic Peninsula, is the fourth-largest ice shelf on the coast of Antarctica. In 2014, a crack that had been slowly growing in the ice shelf for decades suddenly turned northward and accelerated, creating today’s iceberg.

“The interesting thing is what happens next…how the remaining ice shelf responds,” said Kelly Brunt, a glaciologist from NASA’s Goddard Space Flight Center and the University of Maryland. “Will the ice shelf weaken, or possibly collapse like its neighbors Larsen A and B? Will the glaciers behind the ice shelf accelerate and have a direct contribution to sea level rise? Or is this just a normal calving event?”

Scientists have monitored the progression of the rift over the past year using data from the European Space Agency’s Sentinel satellites (which can image with radar during the long Antarctic night) and thermal imagery from Landsat 8 and the MODIS instruments on NASA’s Terra and Aqua satellites.

In the coming months and years, researchers will monitor the response of Larsen C and the glaciers that flow into it with satellite imagery, airborne surveys, automated geophysical instruments on the ice, and field work.

“We don’t currently know what changed in 2014 that allowed this rift to push through the suture zone and propagate into the main body of the ice shelf,” said Dan McGrath, a glaciologist at Colorado State University who has been studying Larsen C since 2008.

McGrath said the growth of the crack is not directly linked to climate change. “The Antarctic Peninsula has been one of the fastest warming places on the planet throughout the latter half of the 20th century. This warming has driven really profound environmental changes, including the collapse of Larsen A and B,” McGrath said. “But with the rift on Larsen C, we haven’t made a direct connection with the warming climate. Still, there are definitely mechanisms by which this rift could be linked to climate change, most notably through warmer ocean waters eating away at the base of the shelf.”

The U.S. National Ice Center will monitor the trajectory of the new iceberg, which is likely to be named A-68. The currents around Antarctica generally dictate the path that the icebergs follow. In this case, the new berg is likely to follow a similar path to the icebergs produced by the collapse of Larsen B: north along the coast of the peninsula, then northeast into the South Atlantic.

NASA Earth Observatory images by Joshua Stevens, using MODIS and VIIRS data from LANCE/EOSDIS Rapid Response. Story by Maria-Jose Viñas, adapted for Earth Observatory by Kathryn Hansen.

Aqua – MODIS

A chunk of floating ice that weighs more than a trillion metric tons broke away from the Antarctic Peninsula


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