Earth Gauge » Climate Number

Climate Number: One Inch per Year

kraus — Mon, 30 Jan 2012 15:15:42 +0000

The extent of the Arctic sea ice, which is usually gauged by its annual minimum extent in September, has been declining by 11.2 percent per decade since 1979. Large-scale effects of this decline impact Earth’s climate, primarily through increased absorption of sunlight by the open oceans. Local effects have also been documented. As ice has melted, the number of open water days along the coasts of the Beaufort and Chukchi Seas around Alaska increased from an average of 45 days in the late 1970’s to about 95 days in recent years. This increased melt means there is less ice protecting and stabilizing the sea cliffs in the region, which has caused increased cliff erosion along these coasts. The sea cliffs are now retreating at a rate of 45 feet per year. Decreased Arctic sea ice has also made the waters in the Chukchi Sea and Pacific-Arctic Ocean choppier. Less ice means that there is a larger area in which waves can develop and a longer ice-free season, allowing for late fall and early winter storms to move over water instead of ice. These developments mean that the average surface wave heights are growing over the Chukchi Sea at a rate of 0.8 inches per year and over the Pacific-Arctic at a rate of one inch per year. In the Chukchi Sea, there were five events in the 2000s when surface wave heights exceeded 13 feet; during the 1990s, only two of these events occurred.

For comparison: Global sea level is rising at about 2.1 millimeters per year, or a little over one-sixteenth of an inch.

Seasons: Winter, Spring, Summer, Fall

Sources: Overeem, I et al. “Sea ice loss enhances wave action at the Arctic coast.” Geophysical Research Letters 38 (2011): L17503 and National Snow and Ice Data Center: Arctic Sea Ice News and Analysis. Accessed Online 28 January 2011 and Francis, OP et al. “Ocean wave conditions in the Chukchi Sea from satellite and in situ observations.” Geophysical Research Letters 38 (2011): L24610.

Climate Number: 1.3 Petawatts

kraus — Mon, 30 Jan 2012 15:12:46 +0000

Discussions of climate and climate variability often focus on temperature trends at the Earth’s surface, which is where humans spend most of their time. But the atmosphere holds onto little energy compared to the oceans – the top few feet of the ocean holds as much heat as the entire atmosphere above it! Transfers and imbalances in ocean heat content drive weather variability on land. The long timescales involved in ocean heat transfer enable forecasters to make predictions on seasonal time scales, and trends in the ocean currents that move ocean heat around hold significant potential for enhancing such predictions. One of the strongest ocean currents is the Gulf Stream, which is part of the larger Atlantic meridional overturning circulation (AMOC), a system of poleward moving warm water at the surface and equatorward moving cold water at the depths from 4,000 to about 16,000 feet down. The AMOC system moves about 1.3 petawatts of heat northward, which helps to keep Europe warmer than other locations at its latitude. Variations in this heat transport, as illustrated by changes in the strength of ocean current flows, can be used to make predictions about future heat distribution patterns in the oceans and thus future weather pattern predominance. Between 2000 and 2010, the stream of cold, equatorward moving deepwater has weakened by about three Sverdrups (30 million cubic meters per second), which represents about a 20 percent decrease.

For comparison: Including energy for transport, manufacturing, heating and cooling, residential electricity, etc., it takes about 324 billion watts to power the United States. That is about 1/4000th of the 1.3 petawatts of power in the Atlantic Ocean’s northward heat transport.

Seasons: Winter, Spring, Summer, Fall

Sources: Energy Information Administration. Annual Energy Review, 2010. Accessed Online 28 January 2012 and Send, Uwe et al. “Observation of decadal change in the Atlantic meridional overturning circulation using 10 years of continuous transport data.” Geophysical Research Letters 38 (2011): L24606.

Climate Number: 17 Miles per Decade

kraus — Mon, 05 Dec 2011 13:29:21 +0000

Temperatures have warmed by an average of two degrees Fahrenheit over Earth’s land surface and 0.6 degrees Fahrenheit over the oceans over the past 50 years. These temperature changes have been accompanied by changes in precipitation and seasonal cycles, including lengthening of the growing/frost-free season in temperate and high latitudes. Together, these factors related to temperature and moisture availability make up the climate envelope of a given area. Every species on Earth has a preferred climate envelope: you don’t find palm trees living in the Arctic or cactuses living in wet temperate zones like the Pacific Northwest. Some species, like plants, cannot easily move to new areas when climatic conditions change rapidly. More mobile species, such as birds, can move readily from one region to another if average conditions become too hot, too cold, too wet or too dry. Over the last 50 years, climate envelopes have moved towards the poles and to higher elevations. In other words, places that used to be too cool for some species are now just right, while the places they used to inhabit have become too warm. The poleward shift of these envelopes has been proceeding at a rate of 17 miles per decade, for a total shift of about 85 miles over the last 50 years.

For comparison: It is about 85 miles from Indianapolis, Indiana to Fort Wayne, Indiana. Small but noticeable temperature differences between these two locations exist.

Seasons: Winter, Spring, Summer, Fall

Source: Burrows, MT et al. “The Pace of Shifting Climate in Marine and Terrestrial Ecosystems.” Science 334 (2011): 652-655.

Climate Number: 1,450 Years

kraus — Mon, 05 Dec 2011 13:27:43 +0000

The September/October Arctic sea ice annual minimum this year was the second lowest minimum on record for the 33 year period of satellite observations. The lowest minimum was recorded in 2007. But how do these ice extents relate to what the sea ice has done over the past several hundred or thousand years? Known relationships between interannual variability of Arctic sea ice and weather in other areas of the Arctic exist – weather influences things like ice accumulation, tree growth and lake sediment deposition. Analysis of ice cores (particularly from the Greenland Ice Sheet), tree rings and core samples taken from lake bottoms can be used to reconstruct the weather in the Arctic and the historical extent of Arctic sea ice. Through this analysis, researchers have pieced together the past 1,450 years of Arctic sea ice, with a record extending back to 561 A.D. The analysis shows that the extent of the Arctic sea ice does not necessarily fluctuate with global temperature trends inferred from other proxy records. For example, sea ice was at a lower extent near the beginning of the Dark Ages Cold Period from 600 to 900 A.D. than it was during the Medieval Warm Period. This suggests that changes in the transport of warm waters from the North Atlantic into the Arctic Ocean have been the primary driver of variability in Arctic Sea Ice extent over the past 1,450 years. The analysis also suggests that shrinking of Arctic Sea Ice over the past few decades and the recent satellite records for minimum extent have no precedent during this 1,450 year period.

Seasons: Winter, Spring, Summer, Fall

Source: Kinnard, C et al. “Reconstructed changes in Arctic sea ice over the past 1,450 years.” Nature 479 (2011): 509-512.

Climate Number: 195 Kelvin (-108.67 degrees Fahrenheit)

kraus — Mon, 31 Oct 2011 15:30:29 +0000

Commercial airline flights spend most the time in the lower reaches of the stratosphere, which is the second layer of the atmosphere beginning at five to six miles up in the air. The air in the stratosphere is thin and cold, making it inhospitable, but it is also less turbulent than the air in the troposphere near the Earth’s surface, which is part of the reason pilots like to fly there. The stratosphere is also where a protective layer of ozone sits. While ozone near the Earth’s surface poses a health hazard to people, ozone in the stratosphere has been protecting life for billions of years. Depletion of stratospheric ozone happens during the respective winters at both poles, as temperatures dip below 195 Kelvin allowing polar stratospheric clouds to form. Within these clouds, conditions are just right for a series of chemical reactions to take place, with the result being the destruction of ozone molecules. This ozone destruction process is more intense around Antarctica, leading to the formation of the famous “ozone hole” around that continent. Ozone concentrations reach their minimum during the Southern Hemisphere spring (September to December), following the peak (June through August) winter ozone destruction season. The same process happens in the Arctic, but not to the same extent. This past winter of 2010-2011, however, featured the lowest ever recorded stratospheric ozone values in the Arctic, although these values are higher than the values regularly experienced over Antarctica during its ozone minimum season. Temperatures at 12.5 miles in altitude over the Arctic remained below 195 Kelvin from mid-December 2010 through the end of March 2011. One climatic trend that may have influenced this first “Arctic ozone hole” is the cooling of the lower stratosphere by 0.5 Kelvin per decade and the cooling of the upper stratosphere by 1.0 Kelvin since 1979. This cooling is related to the warming of the troposphere that occurred during the same period.

For comparison: If 195 Kelvin (-108.67 degrees Fahrenheit) sounds cold, it is! Water boils at 373.16 Kelvin (212 degrees Fahrenheit) and freezes at 273.16 Kelvin (32 degrees Fahrenheit). It is not quite as cold, however, as the lowest surface temperature ever recorded, which was 184.0 Kelvin (-128.6 degrees Fahrenheit) at Antarctica’s Russian Vostok Station in July of 1983.

Seasons: Winter, Spring, Summer, Fall

Sources: Garcia, RR. “An Arctic ozone hole?” Nature 478 (2011): 462-463 and Manney, GL et al. “Unprecedented Arctic ozone loss in 2011.” Nature 478 (2011): 469-475.

Climate Number: 0.40 X 10^22 Joules per Year

kraus — Mon, 31 Oct 2011 15:29:05 +0000

The Earth holds more heat today than it did in 1950 and the lion’s share of this heat has been absorbed by the world’s oceans. Water has a higher specific heat than air or land surfaces, meaning that it takes more energy to raise the temperature of a certain amount (say, a pound) of water than it does to raise the temperature of a pound of air or a pound of most metals. The top 2,300 feet of the world’s ocean waters have been absorbing about 0.40 X 10²² joules of energy per year since 1969, with direct implications for sea surface temperatures and ocean life and indirect implications for global air temperatures, ocean circulation patterns, weather patterns experienced on land and global ice masses.

For comparison: 0.40 X 10²² joules is about ten times the amount of excess energy that is being absorbed by the atmosphere. It is also about nine times the amount of energy in 90 billion tons of oil.

Seasons: Winter, Spring, Summer, Fall

Source: Levitus, S et al. “Global ocean heat content 1955-2008 in light of recently revealed instrumentation problems.” Geophysical Research Letters 36 (2009): L07608.

Climate Number: 5,000,000 cubic feet per second

kraus — Mon, 31 Oct 2011 15:27:22 +0000

Paleoclimatology, the study of past climates and past climate changes, provides ample evidence that climate change can happen suddenly. Around 18,700 years ago, a section of the slowly melting Laurentide (North American) Ice Sheet, which at one point extended all the way from the Arctic to the Ohio River, disintegrated around present day Wisconsin. This disintegration allowed a large lake or lakes, which had formed as the ice sheet had melted and were being held back by ice dams, to quickly drain into the tributaries of the Mississippi River. A surge of glacial melt water on the order of over five million cubic feet per second filled the Mississippi River and traveled all the way to the Gulf of Mexico. The sudden rush of sediment that accompanied this surge settled at the bottom of the Gulf of Mexico. This influx of fresh water likely impacted the Gulf Stream, which is part of a global ocean circulation system driven by differences in temperature and salinity. Changes in the behavior of the ocean circulation system can affect climate and weather throughout the world.

For comparison: The sudden 5,300,000 cubic feet per second surge of freshwater is almost ten times the average flow of the Mississippi River at Baton Rouge, Louisiana, and slightly less than half of the record flow for that location.

Seasons: Winter, Spring, Summer, Fall

Source: Sionneau, T et al. “Provenance of freshwater pulses in the Gulf of Mexico during the last deglaciation.” Quaternary Research 74 (2010): 235-245 and Tarasov, L and Peltier, WR. “A calibrated deglacial drainage chronology for the North American continent: evidence of an Arctic trigger for the Younger Dryas.” Quaternary Science Reviews 25 (2006): 659-688.

Climate Number: 28 Cubic Miles

kraus — Mon, 26 Sep 2011 15:20:29 +0000

Each year the United States pumps about 28 cubic miles of water out its groundwater aquifers – natural underground storage areas – for irrigation, drinking water, industrial purposes, etc. While about 84.6 percent of these withdrawals are recharged to the aquifers through natural recharge (primarily rainfall) or artificial recharge (recharge to the groundwater from human activities), 15.4 percent, or about 4.25 cubic miles, of America’s groundwater withdrawals flow into the oceans without being returned as rainfall. Globally, about 34 cubic miles of groundwater is lost to the oceans every year. While groundwater losses can be replenished over time, losses from arid or semi-arid regions may take thousands of years to recover. Much of the groundwater being pumped from underneath the Great Plains region, for example, is fossil groundwater that was deposited by the melting North American Ice Sheet over 10,000 years ago.

For comparison: The 34 cubic miles of groundwater sent to the oceans raises global sea levels by 0.39 millimeters each year, which is a significant fraction of the total 2.1 millimeter annual sea-level rise. Sea level rise from the water coming off the shrinking Greenland and Antarctic Ice Sheets is about 1.3 millimeters per year.

Source: Church, JA et al. “Revisiting the Earth’s sea-level and energy budgets from 1961 to 2008.” Geophysical Research Letters 38 (2011): L18601.

Climate Number: 5.7 x 1017 joules

kraus — Sat, 27 Aug 2011 21:23:00 +0000

Changes in climate are fundamentally about changes in the amount of energy in the air and water circulating around us. While most discussions of climate trends focus on the air temperature taken at the Earth’s surface, this is only one measure of the amount of energy in the air, let alone the climate system as a whole. The total amount of energy in a parcel of air above the land surface can be broken down into three variables: the kinetic energy, or how much wind is happening inside the parcel; the enthalpy of the air, which is closely related to the temperature measured with a thermometer; and the latent heat, or the energy associated with evaporation and moisture in the air. Generally, the warmest and wettest air parcels are the most energetic. Since at least the early 1970s, the air masses above Earth’s land surface have been gaining energy. There has been a slight “stilling” of winds, meaning a slight decrease in the kinetic energy variable, but this loss has been more than offset by large gains in enthalpy and latent heat content. On average, the surface air (the bottom 6.5 feet of the atmosphere) over Earth’s land surface gained 5.7 x 10¹⁷ joules between 1973 and 2003. In warmer regions, such as the tropics, the largest energy gains have been in latent heat, whereas at the higher latitudes, trends in enthalpy dominated as reflected by the larger temperature increases experienced there.

For comparison: The amount of energy it takes to power the global economy is about 474 exajoules, or 830 times the 5.7 x 10¹⁷ joules the bottom 6.5 feet of the atmosphere over land gained between 1973 to 2003. The amount of energy the top 6.5 feet of the oceans have gained over this same period is about 370 exajoules, about the same as annual global energy use, and the top 2,300 meters of the oceans have gained is 4.2 x 10²² joules worth of energy, or about 90 times annual global energy use.

Seasons: Winter, Spring, Summer, Fall

Source: Peterson, TC et al. “Observed changes in surface atmospheric energy over land.” Geophysical Research Letters 38 (2011): L16707.

Climate Number: 200 Gigatons

kraus — Sun, 21 Aug 2011 16:39:28 +0000

Average global sea level is rising by about three millimeters per year. There are three main contributors to this rise, each of which separately account for about one millimeter each: the thermal expansion of water, or the fact that warmer waters occupies more space than cooler water; the melting of mountain glaciers and ice caps; and the melting of the Greenland and Antarctic Ice Sheets, which are ancient ice masses that sit on bedrock masses near the poles. In Greenland, high rates of surface melt were experienced between 2000 to 2010, with record melt extents happening in 2010 when temperatures were as high as 4.3 degrees Fahrenheit above the 1970-2000 climate normal. During the last decade, Greenland has contributed about 200 gigatons of ice, or around 48 cubic miles of ice into the ocean each year, accounting for about one-sixth of global sea level rise during this period.

For comparison: 200 gigatons is equivalent in volume to 550,000 Empire State Buildings, 38 Lake Okeechobees and 11 Great Salt Lakes.

Seasons: Winter, Spring, Summer, Fall

Source: Mernild, SH et al. “Increasing mass loss from Greenland’s Mittivakkat Gletscher.” The Cryosphere 5 (2011): 341-348.

Climate Number: 15 Million Pounds

kraus — Sun, 21 Aug 2011 16:34:40 +0000

In the air around you are organic aerosols – substances based on carbon-hydrogen bonds that are light enough to be suspended in the atmosphere for days or weeks. How much organic aerosol mass is in the air has direct implications for air quality and human health, as well as for climate and weather. Organic aerosols can help to seed clouds, which can affect how much of the Sun’s energy reaches the surface, and ultimately surface temperatures, rainfall levels and potentially even larger scale circulation patterns. Climate and weather conditions also drive atmospheric aerosol levels, with higher temperatures leading to higher organic aerosol emissions from plants, particularly conifers. In the loblolly pine forests of the Southeast, which cover about 116,000 square miles across 12 states, estimates of emissions of a certain type of volatile organic compound that is particularly important for atmospheric chemistry, sesquiterpenes, are in the range of 15 million pounds for the warm month of September. The amount of sequiterpene emissions increases exponentially with temperature and because organic sources such as pine trees account for as much as 50 percent of fine aerosol concentrations in mid-latitude regions like the southeast, this variance has significant implications for weather and climate variability.

For comparison: 15 million pounds is about the same weight as 80 fully loaded Boeing 737-800s.

Seasons: Summer, Fall

Sources: Horvath, E et al. “Microscopic fungi as significant sesquiterpene emission souces.” Journal of Geophysical Research: Atmospheres 116 (2011): D16301 and Helmig, D et al. “Sesquiterpene emissions from loblolly pine and their potential contribution to biogenic aerosol formation in the Southeastern US.” Environmental Sciences 40 (2006): 4150-4157.

Climate Number: 400,000 Years

kraus — Mon, 06 Jun 2011 14:58:36 +0000

Earth does not orbit the Sun in a perfect circle. Instead, like all the other planets, Earth’s orbit is eccentric, meaning that it moves in a “stretched out” or elliptical pattern. The difference between the perihelion, the point of an orbit when a planet is closest to the sun, and the aphelion, the point of the year when it is the farthest away, defines how eccentric an orbit is. Earth’s orbit is not very eccentric. Earth is about 91.65 million miles away from the Sun at the perihelion in January, and about 94.82 million miles away at the aphelion in July. For comparison, Pluto is about 2.76 billion miles away from the Sun at its perihelion and 4.64 billion miles away at its aphelion, meaning its orbit has pronounced eccentricity. These differences are not constant through time. Earth has 100,000 and 400,000 year eccentricity cycles, which are controlled by the position of the other planets in the solar system. These cycles influence Earth’s climate and are visible in the geologic record, especially from 17 to 13 million years ago during a warm and humid time known as the Miocene Climate Optimum (MCO). During MCO periods of high eccentricity, or periods when the difference between the perihelion an aphelion are greater, seasonal cycles and monsoon circulations are more pronounced. Periods of high eccentricity caused heavier monsoon rains to erode rocks on the Earth’s surface and transport large amounts of calcium carbonate to shallow tropical seas, which is recorded in ocean sediment records. Periods of low eccentricity meant less seasonality and less intense monsoon cycles. Periods of high eccentricity corresponded to periods of higher atmospheric carbon dioxide and higher temperatures while periods with less eccentricity encouraged carbon drawdown into the ocean. A major drop in carbon dioxide levels at around 13.2 million years ago corresponded to an expansion of ice sheets and an end to this particularly warm period.

For Comparison: There were nine complete 400,000 eccentricity cycles during the Miocene Climate Optimum. Earth is currently around the minimum point of this 400,000 year cycle, meaning our orbit is particularly close to a perfect circle and the difference between the perihelion and aphelion is less pronounced.

Seasons: Winter, Spring, Summer, Fall

Sources: Ma, W et al. “Simulation of long eccentricity (400-kyr) cycle in ocean carbon reservoir during Miocene Climate Optimum: Weathering and nutrient response to orbital change.” Geophysical Research Letters 38 (2011): L10701 and Holbourn, A et al. “Orbitally-paced climate evolution during the middle Miocene “Monterey” carbon-isotope excursion.” Earth and Planetary Science Letters 261 (2007): 534-550.

Climate Number: 92 Gigatons

kraus — Mon, 23 May 2011 14:42:55 +0000

The Canadian Arctic Archipelago (CAA), which lies across Baffin Bay from the northwest coast of Greenland, holds about one third of Earth’s ice mass, excluding the giant Greenland and Antarctic Ice sheets. The Archipelago’s 36,500 islands cover 540,000 square miles including Baffin Island, the world’s fifth largest island covering close to 200,000 square miles. The CAA receives relatively little precipitation. This leaves the glaciers that sit on the Archipelago almost entirely at the mercy of summertime temperature variability, as even comparatively wet years do little to offset years with warm summer temperatures and high rates of ice melt. Such high rates of ice melt occurred during the summers from 2007 to 2009, when about 92 gigatons of ice melted each season. This contributed 0.25 millimeters each year to the global three millimeter annual rise in sea level, making the CAA the largest contributor of ice mass to the oceans outside of Greenland and Antarctica. These 92 gigatons represent a significant departure from the 31 gigatons the CAA contributed to the ocean each year from 2004 to 2006. These numbers suggest that each 1.6 degree Fahrenheit rise in summertime temperature results in an additional 64 gigatons of CAA ice loss.

For comparison: 92 gigatons is about the same weight as 250,000 Empire State Buildings.

Seasons: Spring, Summer, Fall

Source: Gardner, AS et al. “Sharply increased mass loss from glaciers and ice caps in the Canadian Arctic Archipelago.” Nature 473 (2011): 357-360.

Climate Number: 23 feet

kraus — Mon, 04 Apr 2011 14:58:52 +0000

How do sea levels vary as the world warms or cools? A warmer planet means more heat is stored in the oceans. More heat causes thermal expansion that pushes ocean waters onto the land. A warmer Earth also means more melting of the ice sheets and alpine glaciers that sit on the land surface, putting this water in the oceans and causing further sea level rise. During the last glacial maximum 20,000 years ago when huge ice sheets extended from the Arctic all the way to the midlatitudes (the North American or Laurentide Ice Sheet covered lands as far south as the Ohio River) sea levels were almost 400 feet lower than today. During a warm interglacial period 125,000 years ago, when global temperatures were close to 3.6 degrees Fahrenheit warmer than today and the poles were as much as nine degrees Fahrenheit warmer than today, sea levels were about 23 feet higher.

For Comparison: When sea levels were 23 feet higher, South Florida was likely under water, as was Louisiana’s Bayou. Cities like Baltimore, parts of Washington, DC, Boston, the Norfolk/Hampton Roads area and the Outer Banks were likely submerged as well. The Jutland Peninsula in Denmark was probably cut off from mainland Europe and enough of Scandinavia would have been submerged to allow the Baltic Sea to join the Arctic Ocean.

Seasons: Winter, Spring, Summer, Fall

Sources: Denton, GH et al. “The Last Glacial Termination.” Science 328 (2010): 1652-1655 and Kopp, RE et al. “Probabilistic assessment of sea level during the last interglacial stage.” Nature 462 (2009): 863-868.

Climate Number: 1670 Petagrams of Carbon

kraus — Mon, 04 Apr 2011 14:56:31 +0000

The northern circumpolar permafrost region – located mostly above 60 degrees North or the southern tip of Scandinavia – is an area where temperatures are so cold that the soil remains permanently frozen, except for an active surface layer that is as shallow as a few inches deep. Beneath this active layer lie ancient carbon stocks composed of partially decayed plants and animals that have remained frozen for thousands of years. Despite comprising only 16 percent of Earth’s total global soil area, these northern circumpolar zone carbon stocks hold about 1670 petagrams, or 1670 billion tons, of carbon. This is about 50 percent of the planet’s total below-ground carbon pool. It is also about twice the amount of carbon held in the atmosphere. Earth’s recent one degree Fahrenheit warming trend has been particularly pronounced in the Arctic region. The Arctic has been warming at twice the global rate since the 1970s and summer temperatures in the Alaskan and western Canadian Arctic have risen by 2.5 degrees Fahrenheit and winter temperatures by 3.6 degrees Fahrenheit. This has corresponded to thawing of deeper soil layers for longer periods of the year and a disturbance of the formerly locked-away ancient carbon. Emissions of this carbon from the soil into the atmosphere have been increasing, although they have been somewhat counteracted by an increase in surface vegetation, which takes more carbon out of the air. Experimental warming of plots in the Arctic shows that increases in thaw depth persist into the following winter, stimulating respiration that doubles the total amount of carbon released annually into the atmosphere.

For Comparison: 1670 Petagrams is about the same mass as 18 million Nimitz Class Aircraft Carriers or 300,000 Great Pyramids at Giza.

Seasons: Winter, Spring, Summer, Fall

Sources: Schuur, EAG et al. “The effect of permafrost thaw on old carbon release and net carbon exchange from tundra. Nature 459 (2009): 556-559 and Schuur, EAG et al. “Effects of Experimental Warming of the Deep Soil and Permafrost on Ecosystem Carbon Balance in Alaskan Tundra.” American Geophysical Union Fall Meeting 2009, abstract #U44A-03 and Tarnocai, C et al. “Soil organic carbon pools in the northern circumpolar permafrost region.” Global Biogeochemical Cycles 23 (2009): GB2023.

Climate Number: 2.7 million years

kraus — Fri, 25 Feb 2011 22:41:56 +0000

The three to seven year El Niño-Southern Oscillation (ENSO) is the periodic warming (El Niño phase) and cooling (La Niña phase) of the eastern tropical Pacific. This warming and cooling is related to a relaxing (El Niño) and strengthening (La Niña) of an upwelling of cold, nutrient rich water from the depths to the surface off the coast of Peru; this upwelling is connected to the strength of the easterly trade winds that blow across the Pacific. Different ENSO phases mean different shapes for the Northern Hemisphere storm tracks that control variability in mid-latitude winter weather. Different ENSO phases also affect the intensity of hurricane seasons in both the Pacific and Atlantic basins. The modern ENSO system may not have always existed, or if it did it operated differently than it does today. The climate of the early Pliocene (about four million years ago) was much warmer than the world we inhabit today, despite there being a similar arrangement of continental land masses and similar species present. During this period, the Pacific was believed to be in a persistent El Niño state. There was an expanded Pacific warm pool then, with virtually all of the tropical Pacific, north to south and east to west, being around the same temperature. The modern ice age, or the current climate of glacial-interglacial cycles, operating on periods of roughly 100,000 years, began about 2.7 million years ago. By this time, the modern ENSO cycle had developed, and a contraction of the warm pool corresponded to reduced air temperatures and increased snowfall over North America, which helped to build up the ice sheet there. The presence of this ice sheet amplified the cooling trend and helped to solidify the presence of the ice age, known as the Pleistocene epoch.

Seasons: Winter, Spring, Summer, Fall

Source: Brierley, CM and Fedorov, AV. “Relative importance of meridional and zonal sea surface temperature gradients for the onset of the ice ages and Pliocene-Pleistocene climate evolution.” Paleoceanography 25 (2010): PA2214.

Climate Number: 2,200 Years

kraus — Mon, 07 Feb 2011 14:49:41 +0000

Imagine a parcel of warm and salty water travelling northward through the North Atlantic Ocean. As it moves, it gradually loses water through evaporation into the atmosphere – this water creates rain in faraway places. As evaporation happens, the parcel of water becomes saltier and denser. By the time it gets to Greenland, it is so dense and has cooled to the point that it can no longer float on the ocean surface. It sinks and becomes “deepwater,” now traveling southward through the Atlantic along the ocean bottom. Eventually, it reaches the southernmost Atlantic and swirls around the Southern Ocean surrounding Antarctica until it is picked up by current in the South Pacific that transports it north. Finally, the parcel resurfaces as warm water in the northeastern Pacific.

Perhaps the most important component of Earth’s climate cycle is the thermohaline circulation, the movement of currents throughout the world’s oceans. The thermohaline circulation affects both the distribution of heat and moisture on the planet’s surface, as well as concentrations of gases in Earth’s atmosphere. Parcels of water on the ocean surface contain levels of carbon in equilibrium with the atmosphere. Once these waters sink, they take carbon with them to the depths. When they resurface, they find a new equilibrium with the atmosphere. Water on the ocean bottom can take a long time to resurface; a deepwater parcel forming in the North Atlantic can spend 2,200 years circulating around the ocean before resurfacing in the Northeast Pacific. These long periods of circulation mean that the oceans can absorb and then store large amounts of carbon for long periods of time.

For Comparison: 2,200 years ago, the Roman Republic declared war on Macedon, beginning the Second Macedonian War. This was also around the time that the Great Wall of China was completed. Around 2,200 years ago, the first accurate estimate of the distance between the Sun and Earth was made by studying lunar eclipses.

Seasons: Winter, Spring, Summer, Fall

(Sources: Thornalley, DJR et al. “The Deglacial Evolution of North Atlantic Deep Convection.” Science 331 (2011): 202-205 and Sarnthein, M. “Northern Meltwater Pulses, CO2 and Changes in Atlantic Convection.” Science 331 (2011): 156-158.)

Climate Number: 150 Teragrams of Carbon

kraus — Mon, 03 Jan 2011 15:22:00 +0000

Tiny particles suspended in the air affect Earth’s temperature by reflecting, absorbing and scattering solar radiation. These tiny particles known as aerosols – generally between ten billionths and 1000 billionths of a meter –are so small that it only takes slight winds to keep them aloft. In addition to affecting solar radiation, aerosols are also critical to key nutrient cycles and even provide surfaces on which raindrops form, making them one type of condensation nuclei. Organic aerosols are a type of aerosol based on carbon and hydrogen bonds. Organic aerosols are produced by combustion (burning), vegetation, oceanic phytoplankton and human industrial activities. Past estimates of the atmosphere’s organic aerosol load have been broad. A recent estimate is 150 teragrams of carbon is emitted from Earth’s land surface each year as part of these organic aerosols. This mass does not include the mass of the hydrogen, oxygen, nitrogen, etc. atoms that are also part of the organic aerosol molecules. These organic aerosols are believed to spend about 21 days in the atmosphere before they fall to the Earth’s surface.

For Comparison: 150 teragrams is about the same weight as 300 fully loaded ultra large crude carrier tanker ships, the largest ocean-going ships in the world.

Seasons: Winter, Spring, Summer, Fall

Sources: Heald, CL et al. “Satellite observations cap the atmospheric organic aerosol budget.” Geophysical Research Letters 37 (2010): L24808 and Ellison, GB et al. “Atmospheric processing of organic aerosols.” Journal of Geophysical Research: Atmospheres 104 (1999): 11633-11641.

Climate Number: 35 millimeters

kraus — Mon, 29 Nov 2010 15:37:43 +0000

Since 1992, satellites have been providing continuous global coverage of changes in ocean surface heights. The first satellite to provide such coverage, TOPEX Poseidon, was launched in 1992. Although only designed to serve for three years, it provided data until 2005. Jason I, TOPEX Poseidon’s replacement, began operating in 2001 and Jason II was launched in 2008. These satellites, by emitting microwave pulses and reabsorbing them after they bounce off the ocean surface, show that the global sea level is rising by an average of three millimeters per year. Although this global average is positive, there are some ocean localities where cooling or a drop in salinity can contribute to a drop in sea level. Differences between local and global sea level trends can also result from shifts in weather patterns that change wind speeds over parts of the ocean; changes in ocean winds cause redistributions of ocean water and local differences in sea levels. A variety of other factors, such as changes in freshwater discharge from land, also contribute to local differences. Overall, the areas with positive trends have outbalanced the areas with negative trends over the past several decades. While three millimeters per year rise is the global average, some areas have experienced periods where sea level rose by much more than this amount. Off the east coast of the Philippines, for example, sea level rose by as much as 35 millimeters per year between 1993 and 2001 (the years with continuous TOPEX Poseidon coverage). Similar values were recorded around the Kuroshio Current region off Japan’s east coast.

For Comparison: 35 millimeters is about 12 year’s worth of current average global sea level rise (three millimeters).

Seasons: Winter, Spring, Summer, Fall

Source: Lombard, A et al. “Regional patterns of observed sea level change: insights from a 1/4 degree global ocean/sea-ice hindcast.” Ocean Dynamics 53 (2009): 433-449.

Climate Number: Two Degrees Fahrenheit

kraus — Mon, 29 Nov 2010 15:34:50 +0000

Earth’s lakes are collecting and storing more heat than they did a century or even several decades ago. One indication of this increased heat storage is a global reduction in the annual duration of lake ice cover. In mid-latitude lakes, the average annual date when enough ice has grown to cover a lake’s surface is arriving 5.8 days later in the year than it did in the middle of the 19th century. The average annual “ice-out” day, or the day when the ice leaves a lake, is now arriving 6.5 days earlier in the late winter/early spring. Less ice cover indicates that the lakes have more heat to lose before they can start to freeze. A more direct measurement of heat storage comes from an analysis of large lake (larger than 193 square miles) nighttime infrared emission data collected by satellites from 1985 to 2009. This data indicates that 167 of Earth’s largest lakes warmed at an average rate of two degrees Fahrenheit per decade over this 25 year period. This warming trend has been most visible in the Northern Hemisphere; lakes in the tropics and Southern Hemisphere showed little or no warming during this period. Lakes in the Southwest, such as Lake Tahoe and The Great Salt Lake, showed the most pronounced trends for United States lakes.

For Comparison: The two degree Fahrenheit warming of large inland lakes between 1985 and 2009 is noticeably larger than the global surface temperature warming of about 0.7 degrees Fahrenheit observed over this same period.

Seasons: Fall, Winter, Spring

Sources: Schneider, P and Hook, SJ. “Space observations of inland water bodies show rapid surface warming since 1985.” Geophysical Research Letters 37 (2010): L22405 and NASA: Goddard Institute for Space Studies. “GISS Surface Temperature Analysis.” 18 February 2010. Accessed Online 28 November 2010 and Benson, BJ and Magnuson, JJ. 2006. North Temperate Lakes Long Term Ecological Research Program, Center for Limnology, University of Wisconsin-Madison, Madison WI.