Observing Climate Change

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Defining Climate Change

The Intergovernmental Panel on Climate Change (IPCC) is a collaborative group of thousands of the world’s greatest climate scientists from 195 different countries. In 1988, these scientists were asked by the United Nations Environmental Programme and the World Meteorological Organization to study, monitor, and predict the Earth’s changing climate. The IPCC produces comprehensive reports approximately every 5 years to be used by government and United Nations leaders in developing policies which address climate change. Explore the IPCC website and access all reports.

You will learn below how important it is to take an international perspective when considering the ethical aspects of global climate change.

The IPCC defines climate change as “a change in the state of the climate that can be identified by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer.”

A region’s climate is characterized by both the average and the extremes in its weather conditions, including temperature and precipitation. For example, climate change is evidenced in a clear trend of increasing or decreasing temperatures over hundreds or tens of thousands of years and an increase in intensity and frequency of severe storm events. These changes are very different from normal day-to-day variations in the weather.

Measuring Climate Change

Global-scale observations of the Earth’s climate system (including temperature, precipitation, and other parameters) started in the mid-19th century. Modern observational techniques include both direct measurements at the ground and remote-sensing measurements from satellites (see Figure 5).

Figure 5: Scientific methods used to detect climate change; a. & b. rooftop weather stations, c. instruments attached to hot air balloons which rise high in the air and descend, making measurements throughout the flight, d. satellite photographs and measurements of storm events, e.—i. collection of ice cores for paleoclimate analysis of trapped air bubbles, and j. analysis of tree rings.1

Ancient climates (paleoclimates) can be reconstructed as far back as hundreds of thousands of years by studying ice cores, tree rings, and seafloor sediments (see Figure 5). Together, These reliable detecting methods provide a comprehensive view of the changes in our climate system.

Figure 6. Vostok ice core record of temperature and carbon dioxide during the last 800,000 years. The temperature scale is for warming and cooling in Antarctica and is reconstructed from analysis of stable isotopes in bubbles of air trapped in the core when this part of the ice core froze.1

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    International Geosphere-Biosphere Programme. Modified from Loulergue et al. (2008) and Lüthi et al. (2008).

The climate of our planet has varied throughout its history. The Vostok ice core study (see Figure 6) shows that our world has experienced cycles of warming and cooling 100,000 years apart. These cycles are consistent with changes in the Earth’s orbit around the Sun. However, observation shows that climate change since the mid-18th century has far exceeded these natural cycles. As stated by the IPCC in 2013, “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.”

You will learn below that another kind of measurement—your ‘carbon footprint—is an important part of an ethical response to global climate change.

 
Temperature

Between 1880 and 2012 the average temperature of the Earth’s surface has risen by 0.85°C (1.53°F), as shown in Figure 7. This warming trend has been accelerating. For example, the rate of warming over the 50 years from 1956 to 2005 is 0.128°C per decade— nearly twice that of the 0.074°C per decade rate for the 100 years between 1906 to 2005. This increase in Earth’s average surface temperature is often called global warming.

global mean temperature

Figure 7: Annual global average observed temperatures (black dots) along with simple fits to the data. The left hand axis shows anomalies relative to the 1961 to 1990 average and the right hand axis shows the estimated actual temperature (°C). Linear trend fits to the last 25 (yellow), 50 (orange), 100 (purple) and 150 years (red) are shown. Note that for shorter recent periods, the slope is greater, indicating accelerated warming.1

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    PCC, 2013: Climate Change 2013: The Physical Science Basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, FAQ 2.1, Figure 1; FAQ 3.1, Figure 1. [Stocker,T.F., D.Qin, G.-K. Plattner, M.Tignor, S.K.Allen, J.Boschung, A.Nauels, Y.Xia, V.Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, UK and New York, USA.

This global temperature increase greater at higher northern latitudes, as shown by the orange shading in Figure 8. This greater and more rapidly changing Arctic temperature is referred to as “Arctic Amplification”. This phenomenon occurs because snowmelt now begins earlier in northern regions due to climate change. Earlier loss of snow cover decreases Earth’s albedo— the reflection of solar energy by Earth’s surface back to outer space. As a result, more sunlight is absorbed by Earth’s surface which results in further heating the land and air in polar and mountainous regions. Like the Mongolian herders discussed at the beginning of this chapter, people living in northern countries are experiencing Arctic Amplification today.

Temperature Anomaly

Figure 8: Global temperature anomalies for 2000 to 2009. Temperature anomalies do not depict absolute temperature, but rather how much warmer or colder a region is compared to the norm for that region from 1951 to 1980. Global temperatures from 2000–2009 were on average about 0.6°C higher than they were from 1951– 1980. The Arctic, however, was about 2°C warmer.1

Sea Level Rise

Increases in sea level are also consistent with global warming. In the last century, the global average sea level rose 1.7 mm (0.067 inches) per year. Since the 1990s, the rate of sea level rise has increased to 3.1 mm per year (see Figure 9). This increase has been caused by two factors: 1) thermal expansion of the oceans as the water becomes warmer, 2) added water from the melting of land ice, including glaciers and ice caps. Both factors are linked to global warming.

Global Mean Sea Level

Figure 9. Changes in global average sea level since 1880. Data from coastal tide gauges and satellite altimeter observations were combined to provide the blue line (averages) and shaded blue area (depicting the variability). Changes since 1993 from satellite altimeter data alone are in red.1

Retreat of Ice Caps

Satellite data show that each year the area of Arctic sea ice has been shrinking, with larger decreases observed in the summer (see Figure 10).

Arctic Ice Caps

Figure 10. Decline of Arctic ice cap from 1980 (left) to 2012 (right). The bright white central mass shows the perennial sea ice while the larger light blue area shows the full extent of the winter sea ice, including the average annual sea ice during the months of November, December and January.1

The average rate of Arctic ice loss since 2000 is about four times higher than the rate seen in the 1990s (see Figure 11). James Balog, a National Geographic fellow and photographer, has used time lapse photography to visually document the melting of the worlds largest glaciers and ice fields. Learn more by viewing James Balog’s TED talk.

Figure 11. Decline of Arctic summer sea ice extent since 1900.1

Glaciers and snow cover on average have also declined in the Northern Hemisphere since the mid-20th century. For example, the Northwestern Glacier in Alaska has retreated dramatically during that time. In addition, both the thickness and the extent of permafrost have experienced considerable reductions in the tundras of Northern Alaska and Russian European North since the 1970s. Permafrost is any soil or rock that remains frozen—below 32°F—throughout the year. For a soil to be considered permafrost, it must be frozen for at least two consecutive years or longer. Permafrost can be found in cold climates where the mean annual temperature is less than the freezing point of water. Such climates are found near the North and South poles and in some alpine regions. Tundras are vast northern “wetlands’ whose organic carbon-rich soils are permanently frozen. The melting of tundra permafrost accelerates climate change because permafrost melting causes anaerobic decomposition to occur in the tundra soils, the by-product of which is methane. Methane is a GHG 20 times more potent at trapping heat than CO2, so release of methane from the melting tundra soils has a positive feedback. Melting releases CH4 which enhances more warming in the atmosphere, resulting in greater melting of the tundra. Permafrost melting and subsequent methane release is another component of Arctic Acceleration.

From what you learned in Chapters 2 and 3 about the spiritual significance of water and food, you can see how global climate change impacts the sacred dimension of not only the air we breathe, but also the water we drink and food we eat.