Geography discussion 1

This is likely to be one of the most well-cited pictures of Earth called “Blue Marble”. It was taken on December 7, 1972, by the crew of the Apollo 17 spacecraft. It has a distinct color of blue, because the Earth uniquely carries an atmosphere and 70% of the Earth’s surface is covered by the ocean.

Atmosphere from Space

We can see our atmosphere even from space. In this figure, the bright layer is the atmosphere between space and Earth; both are shown here in black. Please note how thin the atmospheric layer is relative to Earth’s diameter!

Another view of the Atmosphere from Space

This is a zoomed-in image of the atmosphere. You will notice that there is a gradual color change ranging from a brownish color closer to the Earth’s surface that transitions to a pale blue and eventually fades into space. The atmosphere extends about 10,000km into space. There is no exact top to the atmosphere. Due to the Earth’s gravity, the number of molecules, which individually each carry mass, gradually decreases outward into space. Most of the gas molecules are within the lower atmosphere. 90% of the atmosphere’s mass is in its lower 10km and 99.9997% is within the lower 100km. You will also notice that there are little blobs in the brownish colored layer close to the surface. This layer is called the troposphere, the lowest layer of the atmosphere ranging from 6-10km above sea level. This is where we live, clouds are formed, daily weather is observed, and the majority of the molecules exist. The blobs you see are seemingly giant cumulonimbus – dense towering clouds – often associated with thunderstorms.

Composition of the Atmosphere including variable components (by volume)

The three elements that make up over 99.9% of the atmosphere – nitrogen, oxygen, and argon. These elements are abundant in the atmosphere and have many uses.

Pure nitrogen (N2) is used in its very cold, liquid state as it boils at -195.8 C (or -320F). Ted Williams, a baseball player who played for the Boston Red Sox for 22 years, and deceased in 2002, is preserved in liquid nitrogen since his family members chose to have his remains frozen.

Pure oxygen (O2) is used to achieve higher temperatures, to increase the efficiency of waste incinerators. It is also used as an oxidizing agent, and in medical applications to assist and sustain a person’s respiratory functions.

Argon (Ar) is a colorless, odorless, nontoxic, and nonreactive gas. It creates inert environments for growing crystals, often used in semiconductors. It protects materials against corrosion. It also fills the air space in double-pane insulating windows.

Earth’s climate system and interactions of its

components

Two key ideas for this course, especially for the first half is:

1st: Climate is regulated by complex interactions amongst components of the Earth’s system.

2nd: Understanding climate change can be reduced to understanding how “the control knobs” function

Climate change

The knobs that control earth’s climate: • Atmospheric composition (greenhouse effect) • Amount of solar radiation (luminosity) • What parts of Earth get radiation (orbit) • Atmospheric and ocean circulation • Earth’s albedo (fraction of solar energy reflected off earth’s

surface) • Volcanoes • Plate tectonics

Greenhouse Effect

We are here.

First, a bit about radiation . . .

How the control knobs work

Amount of energy reaching earth determines the climate. Dominant source of energy is sunlight, which when reaching Earth can heat the land, ocean, and atmosphere.

If a chunk of matter oscillates and interacts with light at all possible frequencies, it is called blackbody. And the light (energy) that is emitted by a blackbody is called blackbody radiation. In this manner, although “blackbody” is originally named for an ideal object, we consider the Earth as a blackbody. In fact, many objects that radiate energy back when they are heated are considered as a blackbody.

The Greenhouse Effect Greenhouse gases don’t “trap” heat; they absorb heat and re- radiate it out to space and back to Earth.

So, some of that sunlight is reflected back to space by the Earth’s surface, clouds, or ice. But much of the sunlight that reaches Earth is absorbed and warms the planet. When Earth emits the same amount of energy that it absorbs, its energy budget is in balance, and its average temperature remains stable.

The discrepancy between incoming solar energy and outgoing radiation energy is the greenhouse effect. Earth’s atmosphere contains greenhouse gases (e.g. CO2, CH4, etc.) that absorb 95% of the longwave (we will learn more about this later) back radiation emitted from the surface.

Earth’s radiation budget

Here is a breakdown of the numbers… Solar radia)on arriving at the top of Earth’s atmosphere averages 342 W/m2, indicated here as 100% (upper leB). About 30% of the incoming radia)on is reflected and scaHered back into space, and the other 240 W/m2 (70%) enters the climate system. Some of this entering radia=on warms Earth’s surface and causes it to radiate heat upward (right). The greenhouse effect (lower right) retains 96% of the heat radiated back from Earth’s heated surface and warms Earth by 31 C̊.

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http://berkeleyearth.org/2018- temperatures/

(Upper figure) Mean global air temperature variation from 1850 to 2018 In 2018, 9 of the 10 warmest years have occurred since 1990.

(Lower figure) Atmospheric CO2 variation during the same interval From 1960 to present: the atmospheric CO2 concentration has been measured in Mauna Loa, Hawaii. Before 1960, the CO2 concentration is a reconstructed value based upon CO2 preserved in ice cores.

Ice core records

Temp.

CO2

Dust

Annually laminated

bands within ice

core

Thousands of years ago

Why do we use ice core records instead of observed data (which seems to be the more direct and reliable approach)?

This is because, unfortunately, we only have a limited number of observed records for us to understand the natural cycle of the Earth’s climate – most of the data are available only for the past 50 years of which a few extend past a couple hundred years. This means, for instance, if we would like to discuss our climate system in relation to the El Nino cycle, which likely occurs every 3-5 years on average, we can only refer to a few of those events. For this reason, we need a longer record than the observational record.

By using ice core records, as shown in this figure, we can study and argue climate/environmental variability of the past 400,000 years. If the ice core preserves annual layers (like tree rings), the record you are looking at is basically a sub-seasonal resolution of climate variability.

Climate Change in New England

Weider and Boutt, 2010

What is happening in New England?

This figure shows 12 month moving averages of temperature data

measured at 43 observational sites across New England between

1920 and 2009. Please note that this data is an average of 12

months, and any seasonal variability is expressed much less obvious.

There maybe a warming trend? This may be correct. However,

importantly, local temperature variability can be quite different from

global temperature variability – it maybe even cooling in some areas.

Receding mountain glacier due to recent warming.

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World Population (http://www.census.gov/ipc/www/idb/worldpopinfo.html)

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Today 7 billion

Is this temperature trend related to population growth?

Popula'on growth

If so, what will the future population be? Check today’s population: https://www.census.gov/popclock/

MMD-A1B 2080-2099 vs 1980-1999 IPCC 2007

Effects on Agriculture and the Ocean?

Also figures from the IPCC (Intergovernmental Panel on Climate Change) showing the discrepancy between simulated climate model results 2080-2099 and observational data 1980-1999. Precipitation, soil moisture, runoff, and evaporation. Some areas experience drier conditions.

Source: IPCC 2007

Black line: observed temperatures Blue: expected changes due to natural factors Pink: expected changes due to natural factors plus greenhouse gases

Comparison of observed continental- and global-scale changes in surface temperature with results simulated by climate models using either natural or both natural and anthropogenic forcings. Averages of observations are shown for the period 1906-2005 (black line) plotted against the center of the decade and relative to the corresponding average for 1901-1950. Lines are dashed where spatial coverage is less than 50%. Blue shaded bands show the 5 to 95% range for 19 simulations from five climate models using only natural forcings due to solar activity and volcanoes. Red shaded bands show the 5 to 95% range for 58 simulations from 14 climate models using both natural and anthropogenic forcings (like CO2)

Change in Snow Depth CRCM-A2 2070 Results from another climate model showing changes in snow depth in

North America.

An example of a positive feedback

Warming reduces the cover of snow and sea ice in the Arctic from 2005 (right) to 2007 (left), increases the amount of heat absorbed by exposed water, reduces albedo, and thereby further warms the climate. This is called a positive feedback process.

We will learn more about “albedo” and “feedback process” later this semester.

November Arctic Ocean Ice Extent

Source: NSIDC

Monthly November ice extent for 1979 to 2014 shows a decline of 4.7% per decade relative to the 1981 to 2010 average.

Source: Steffen et al., 2008

Area of Melting on the Greenland Ice Sheet: increasing Greenland ice sheet is also increasingly melting from 1979 to 2008.

Maps of maximum annual surface melt on the Greenland Ice Sheet derived from monthly ice surface temperature product of Greenland (2000-2016). Greenland ice sheet is also increasingly melBng!

A Multilayer Surface Temperature, Surface Albedo, and Water Vapor Product of Greenland from MODIS, April 2018, Remote Sensing 10(4):555, DOI: 10.3390/rs10040555

This figure shows the amount of ice sheet lost in Greenland and Antarctica between 2002 and 2009.

Velicogna (2009), Geophysical Research Letters, v.36. L19503, DOI: 10.1029GL040222

https://www.antarcticglaciers.org/2020/01/what-is-the-ice- volume-of-thwaites-glacier/

Ice streams of Antarctica

Recent observations show that incursions of warm ocean water cause melting of the undersides of floating ice shelves in West Antarctica. This could cause a rapid and irreversible rise in sea level. Reference: Hillenbrand, CD., Smith, J., Hodell, D. et al. West Antarctic Ice Sheet retreat driven by Holocene warm water incursions. Nature 547, 43– 48 (2017). https://doi.org/10.1038/nature22995

Our own UMass faculty, Prof. DeConto published in Nature journal in 2021 a suggestion that if emissions continue at their current pace, by approximately 2060, the Antarctic Ice Sheet will have crossed a critical threshold that will cause irreversible global sea level rise within a human timescale. Reference: DeConto, R.M., Pollard, D., Alley, R.B. et al. The Paris Climate Agreement and future sea- level rise from Antarctica. Nature 593, 83–89 (2021). https://doi- org.silk.library.umass.edu/10.1038/s41586-021- 03427-0

Future Sea Level? If we lose all ice in the world – what will happen to the sea level?

Bamber et al., 2009

A simula)on model result shows what happens to the sea level, if all sea ice/con)nental ice (ice sheet) fully collapsed. Most of the northern hemisphere experiences an increase in sea level of over 1 m.

What happens with 1 m sea level rise?

Here are links that include recent research outcome about ice loss from

Earth’s ice sheets. Check out the amazing and disturbing videos in this NASA

briefing….

Snow over Antarctica Buffered Sea Level Rise during Last Century

https://go.nasa.gov/2GeaWZb

Carbon Brief.org

http://www.carbonbrief.org/blog/2015/08/new-nasa-videos-show-stark-ice-

loss-from-earths-ice-sheets/

Annual Arctic sea ice minimum 1979-2018 with area graph

https://climate.nasa.gov/climate_resources/155/video-annual-arctic-sea-

ice-minimum-1979-2018-with-area-graph/

Antarctic ice loss: 2002-2016

https://climate.nasa.gov/climate_resources/154/video-antarctic-ice-loss-

2002-2016/