What is some of the most convincing evidence for climate change? Final Version

I believe that a brief understanding of the earth’s climate history and greenhouse gases is essential to interpreting the evidence of warming and climate change.  Throughout history our planet ahs undergone multiple phases of change.  However, this doesn’t mean we should ignore our current situation.  Just because the planet was warmer in the past, does not mean that we should ignore modern climate change.  Studies show that there are a few key factors that contribute to climate change. Factors such as, extremely small variations in Earth’s orbit, which change the amount of solar energy our planet receives, which in turn contributes to climate change.  The current trend of warming is particularly worrisome and noteworthy because it is it occurring at an unprecedented rate not seen in the last 1,300 years; as a result of human activities.

History of Earth’s Climate Change:

Throughout history the earth’s climate has undergone tremendous change.  There are two distinct stages that accurately characterize earth’s climate:  greenhouse and icehouse.  During a greenhouse stage, there is little to no, permanent ice on both the south and north poles.  Warm temperatures are also found at high latitudes.  An icehouse climate is characterized by cool temperatures, cold enough to sustain large ice sheets at both poles.  The planet has transitioned between these two phases only a few times over the past 540 million years.  The most recent of these changes took place during the Cenozoic Era, which was approximately 56 million years ago.  It its extremely important that we have a brief understand of the history of earths climate; in order to analyze current evidence supporting global warming and climate change as an issue. The sudden end of the last ice age about 7,000 years ago, marks the beginning of the modern climate period.  We currently inhabit an icehouse earth, which is comparatively colder to other periods in earth’s history.

Greenhouse Gasses:

The overall levels of greenhouse gases have increased over time. Source: WWF Global
The overall levels of greenhouse gases have increased over time.
Source: WWF Global

Many chemical compounds in Earth’s atmosphere behave like greenhouse gases.  Many gases are naturally occurring while others are synthetic and man made.  Carbon dioxide and other greenhouse gases have a heat trapping nature. They allow direct sunlight to reach the earth’s surface. Greenhouse gases absorb this energy, which allows less heat to escape back to space, and traps it in the lower atmosphere.  Their propensity to affect the transfer of infrared energy through the atmosphere is the scientific basis of many studies and arguments that, increased levels of greenhouse gases cause the Earth to warm in response. Atmospheric concentrations of both the natural and synthetic gases have been rising at an alarming rate over the last few centuries due to the industrial revolution. Also, as the global population has increased; our reliance and use of fossil fuels has increased.  Therefore, emissions of these gases has increased.  Even though carbon dioxide is naturally occurring in the atmosphere, our interference with the carbon cycle through burning forest lands, mining and fossil fuel consumption.  We are artificially manipulating carbon from solid storage to its gaseous state (sublimation).  This increases atmospheric concentrations, which contributes to global warming.

 

The chart shows different types of gases. Source: NOAA
The chart shows different types of gases.
Source: NOAA

Studies conducted by the World Resources Institute indicate that human beings are responsible for contributing 2.3 trillion tones of carbon dioxide to the atmosphere, in only the last 200 years!  Greenhouse gases are being emitted due to human activity at  a groundbreaking rate.  At this current trend, we have already increased the overall atmospheric carbon dioxide by 3.1%.  As a result, fossil fuel emissions and in particular CO2 emissions are 12 times larger when compared to emission levels 24 years ago.  It is now not even surprising that our climate has changed so drastically in an comparatively minuscule time period.

“Scientific evidence for warming of the climate system is unequivocal.”

– Intergovernmental Panel on Climate Change

There is currently a plethora of evidence that supports the notion that our earth is warming and the climate is charging. Evidence such as increased sea levels, global temperature rise, warming oceans, shrinking ice sheets, declining arctic sea ice, glacial retreat, extreme weather events, ocean acidification, and decreased snow cover.  Nonetheless, I want to focus on two specific areas and go in-depth and examine the cause and effect of these two factors on the planet.  Global temperature rise and shrinking ice mass are indisputable pieces of evidence that I will focus on and discuss further.

Global Temperature Rise:

The World is undeniably getting hotter; whether the cause is due to human activities or environmental variability and cyclical events.  Numerous studies have indicated the occurrence of this trend. According to the Intergovernmental Panel on climate change, “temperatures warmed roughly 1.53 °F between 1880 to 2012 across land and ocean surfaces.”  In a 30-year time period ranging from 1983 to 2012, the earth has experienced the warmest temperatures ever in the last 1,400 years.  So, why are temperatures rising globally?  These changes are largely a result of human activities such as burning fossil fuels and increasing levels of greenhouse gasses such as CO2.  Since the industrial revolution mankind has been using fossil fuels on an unprecedented scale.   Fossil fuels emit CO2 because they are carbon based; subsequently when burned and utilized as an energy source, the CO2 stored inside these elements are released.  CO2 and other greenhouse gases contribute to the greenhouse effect and the ‘blanket’ surrounding the earth.  The greenhouse effect refers to the process in which the sun emits short wavelengths of visible light that pass through transparent areas in the atmosphere and are absorbed.  This transparent medium exits because this medium is transparent to the visible light.  This transparency is due to the available electrons; the photons of visible light do not have enough quantum energy to get the electrons to the necessary available energy level.  So therefore the visible light is not transparent in the infrared.  The longer wavelengths of the re-radiated heat from earths heated surface are unable to pass through the transparent medium and are thus trapped in the atmosphere.  This phenomenon explains why sunlight will warm up the interior of your car and stay trapped inside. Visible light passes easily through the clear windshield; while the ultraviolet light is blocked by the glass because of their greater quantum energy. When the longer wavelengths are trapped, this leads to increased heating and results in higher temperatures.  Carbon dioxide in the atmosphere only exacerbates this issue.  Due to is inherent heat trapping properties, CO2 effectively absorbs infrared and prevents significant amounts from escaping back into space.

Global average temperature since 1880. The range of uncertainty is represented by the gray vertical bars. The blue line tracks the changes in the trend over time. source:NOAA National Climatic Data Center
Global average temperature since 1880. The range of uncertainty is represented by the gray vertical bars. The blue line tracks the changes in the trend over time.
source:NOAA National Climatic Data Center
The Graph illustrates earth's CO2 levels over a period of time. Source: NASA
The Graph illustrates earth’s CO2 levels over a period of time.
Source: NASA

Some may ask, “what are the potential consequences of such a drastic temperature rise, if any?”  There are many detrimental effects of global temperature increases that pose a tremendous threat to our planet.  Firstly, our agricultural system would be forever impacted.  Crops need certain and very specific conditions to grow and thrive.  If temperatures continue to rise, some plants will simply stop growing.  Our food resources are very much so in jeopardy if this trend continues.  Climate change will dwindle our current water supply by drying out bodies of water.  Precipitation patterns will be altered, causing  increased incidence of droughts and groundwater depletion.  Climate  change contributes to species extinction and loss of biodiversity through habitat destruction.  As the earth becomes water and water supplies continue to dwindle, wildfires will not only become more common, but also much more destructive.  This will also contribute a large amount of habitat and ecosystem destruction.

Disappearing Ice:

The Ross Ice Shelf Source: Google Images
The Ross Ice Shelf
Source: Google Images

Ice covers approximately 10% of the Earth’s total surface area.  Ice sheets are pieces of glacial mass that stretch for more than 20,000 square miles.  Today, there are two major ice sheets located in Greenland and Antarctica.  Unfortunately, these significant sheets are disappearing expeditiously!  The Antarctic ice sheet is composed of more than 7.2 cubic miles of ice and extends for more than 5.4 million square miles.  To put this into perspective, an ice sheet of this size is approximately the same area of Mexico and The United Sates!  However, the ice shelves lose about 134 billion metric tons of ice annually.  Greenland’s ice sheet is also substantially large; extending 656,000 square miles, covering about 82% of Greenland.  This is equivalent to three times the size of Texas!  During the summer melting period, in an observed period between 1979 to 2006, melting on the ice sheet increased as much as 30!  This rate of melting contributes to the annual ice loss of about 287 billion metric tons.  Due mostly to rising global temperatures the ice is melting.  Sunlight and temperature are generally the two main factors that control the amount of ice and general melting patterns.  Therefore, as temperatures continue to rise, it is no surprise that we continue to observe ice mass loses.   However, another factor is thermal expansion of oceans that contributes to the destruction of sea ice. As seawater warms it expands.  In other words, this leads to an increase of ocean volume, the water now takes up more space in the ocean basin and sea levels rise as a result.

A schematic illustrating the gradual decline of Antarctic ice mass over time. Source:Google Images
A schematic illustrating the gradual decline of Antarctic ice mass over time.
Source:Google Images

I will also mention sea ice because it plays an extremely vital and important role in regulating our climate.  Sea Ice is extremely effective at reflecting incoming solar radiation.  This ability is known as albedo, which indicates how effectively any given surface can reflect sunlight.  Sea ice is capable of reflecting 90% of the sun’ radiation, which really illustrates its effectiveness at reflecting solar radiation.    The Sea ice regulates temperatures by keeping them low through the albedo effect.  If there is less ice and more exposed ocean surface, the cold climates of the artic and Greenland will become warmer!

Arctic Sea Ice Depletion Source: Google Images
Arctic Sea Ice Depletion
Source: Google Images

Glaciers, are dynamic nature, responding to climate variation, revealing the effects and evidence of climate change. According to The World Glacier Monitoring service, Glacial retreat is occurring throughout the world. It is happening in areas such as the Alps, Himalayas, Rockies and Andes mountain ranges! But why are they melting? The retreat is due to serval factors, such as increasing summer temperatures and a sharp reduction in the winter snowpack. The snowpack is essential in forming and maintaining the glaciers. The mean average annual temperature has increased. Spring and summer temperatures have also increased. This causes an earlier snow melt during the summer. Additionally, rain has taken place as he dominant form of precipitation rather than snow. As a result glaciers have continued to shrink, indicating that the snowpack is not adequate to counteract the temperature changes and preserve the integrity of the glacier.

The image shows the retreat of the Gangotri Glacier in the Himalayas since 1780 Source: NSIDC
The image shows the retreat of the Gangotri Glacier in the Himalayas since 1780
Source: NSIDC

Conclusion:

After a large amount of research there are many different deductions and interpretations that can be derived.  Firstly, there is concrete and scientifically backed evidence that climate change and global warming is occurring.  One cannot argue against the vast plethora of evidence and quantitative figures that indicate our climate is in a dire situation.  I don’t believe one single factor is the most convincing evidence of global warming. I think all are equally important and when these different factors are combined together, they are the root cause of the issue at hand.  For example, rising temperatures contribute to melting ice mass which causes rising sea levels.  It is important to realize all these incidents of climate change are interconnected to each other.  Even in some cases dependent on one occurring for the other to happen.  If we as humans can develop a way to control and mitigate our negative impact and footprint on the environment, we may have a chance at bettering our current situation.

Sources:

  1. http://climate.nasa.gov/evidence/
  2. http://www.wunderground.com/climate/SeaIce.asp
  3. https://www2.ucar.edu
  4. https://nsidc.org
  5. http://wwf.panda.org/about_our_earth/aboutcc/problems/weather_chaos/temp_weather/
  6. https://nsidc.org/cryosphere/seaice/processes/albedo.html
  7. http://ete.cet.edu/gcc/?/icecaps_icesheets
  8. https://nsidc.org/glims/glaciermelt/
  9. http://www.climatecentral.org/gallery/graphics/co2-and-rising-global-temperatures

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