Climate Change Concerns

Figure 1. Annual Arctic sea ice minimum since 1979.[5]

Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions.

Global warming is the rise in the average temperature of Earth’s atmosphere and oceans since the late 19th century and its projected continuation. Since the early 20th century, Earth’s mean surface temperature has increased by about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980.[1]

Changes in climate not only affects average temperatures, but also extreme temperatures, increasing the likelihood of weather-related natural disasters. One way in which global warming could impact hurricanes is by making them more intense. More heat and water in the atmosphere and warmer sea surface temperatures could provide more fuel to increase the wind speeds of tropical storms.

North America has seen the world’s sharpest increase in the number of natural catastrophes during the past 32 years, a trend that in some aspects is linked to manmade global warming. According to global reinsurance giant Munich Re, a report released 17 October 2012, examined natural disaster losses between 1980 and 2011, finding that weather-related loss events in North America “nearly quintupled” during the period, compared to just an increase factor of two in Europe.[2]

In May 2014, the U.S. Global Change Research Program released the Third National Climate Assessment, the authoritative and comprehensive report on climate change and its impacts in the United States. The report confirms that climate change is affecting every region of the country and key sectors of the U.S. economy and society, underscoring the need to combat the threats climate change presents and increase the preparedness and resilience of American communities.[3]

Figure 1. Annual Arctic sea ice minimum since 1979.
The image to the top right demonstrates declining Arctic sea ice: 1979-2010. Changes in Arctic sea ice are an indicator of climate change. Observations from NASA satellites show that Arctic sea ice is now declining at a rate of 11.5 percent per decade, relative to the 1979 to 2000 average. Arctic sea ice reaches its minimum extent each September. This time series, based on satellite data, shows the annual Arctic sea ice minimum since 1979. The September 2010 extent was the third lowest in the satellite record.[4]

Causes Global Climate Dashboard[7]
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Climate change is caused by factors that include oceanic processes (such as oceanic circulation), biotic processes, variations in solar radiation received by Earth, plate tectonics and volcanic eruptions, and human-induced alterations of the natural world; these latter effects are currently causing global warming, and “climate change” is often used to describe human-specific impacts.

Whether the initial forcing mechanism is internal or external, the response of the climate system might be fast (e.g., a sudden cooling due to airborne volcanic ash reflecting sunlight), slow (e.g. thermal expansion of warming ocean water), or a combination (e.g., sudden loss of albedo in the arctic ocean as sea ice melts, followed by more gradual thermal expansion of the water). Therefore, the climate system can respond abruptly, but the full response to forcing mechanisms might not be fully developed for centuries or even longer.[6]

Human Influences

Atmospheric concentrations
of CO2[9]
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Throughout its long history, Earth has warmed and cooled time and again. Climate has changed when the planet received more or less sunlight due to subtle shifts in its orbit, as the atmosphere or surface changed, or when the Sun’s energy varied. But in the past century, another force has started to influence Earth’s climate: humanity.

Of most concern in these anthropogenic factors is the increase in CO2 levels due to emissions from fossil fuel combustion, followed by aerosols (particulate matter in the atmosphere) and cement manufacture. Other factors, including land use, ozone depletion, animal agriculture and deforestation, are also of concern in the roles they play – both separately and in conjunction with other factors – in affecting climate, microclimate, and measures of climate variables.

Human activities result in emissions of four long-lived greenhouse gases (GHGs): CO2, methane (CH4), nitrous oxide (N2O) and halocarbons (a group of gases containing fluorine, chlorine or bromine). Atmospheric concentrations of GHGs increase when emissions are larger than removal processes.

Global atmospheric concentrations of CO2, CH4 and N2O have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years (see image right for C02 values).

The Intergovernmental Panel on Climate Change (IPCC), latest report (Fifth Assessment Report – Climate Change 2013: The Physical Science Basis)provided “unequivocal” evidence that since 1950 the atmosphere and oceans had warmed, and that scientists were now “95 per cent certain” that humans were the “dominant cause”. These patterns had been replicated across the climate system, as the amount of snow and ice had diminished, the mean global sea level had risen and concentrations of greenhouse gases had increased.[8]

Climate Change Evidence

Temperature Changes Past
1000 years[10]
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Key Points

  1. Both natural and human factors change Earth’s climate.
  2. Before humans, changes in climate resulted entirely from natural causes such as changes in Earth’s orbit, changes in solar activity, or volcanic eruptions.
  3. Since the Industrial Era began, humans have had an increasing effect on climate, particularly by adding billions of tons of heat-trapping greenhouse gases to the atmosphere.
  4. Most of the observed warming since the mid-20th century is due to human-caused greenhouse gas emissions.
Agency Name Description
NASA’s Global Climate Change
Global Climate Change is produced by the Earth Science Communications Team at NASA’s Jet Propulsion Laboratory/California Institute of Technology. Website:
NASA’s State of Flux Gallery
The State of Flux gallery features images of different locations on planet Earth, showing change over time periods ranging from centuries to days. Some of these effects are related to climate change, some are not. Some document the effects of urbanization, or the ravage of natural hazards such as fires and floods. All show our planet in a state of flux. Website:
NOAA’s National Climatic Data Center (NCDC)
NOAA’s National Climatic Data Center (NCDC) is responsible for preserving, monitoring, assessing, and providing public access to the Nation’s treasure of climate and historical weather data and information. NOAA’s National Climatic Data Center (NCDC) maintains the world’s largest climate data archive and provides climatological services and data to every sector of the United States economy and to users worldwide. Records in the archive range from paleoclimatic data to centuries-old journals to data less than an hour old. The Center’s mission is to preserve these data and make them available to the public, business, industry, government, and researchers.
NOAA is a source of timely and authoritative scientific data and information about climate. Their goals are to promote public understanding of climate science and climate-related events and to make our data products and services easy to access and use. Website:
United Nations Environment Programme – World Glacier Monitoring Service
For more than a century, the World Glacier Monitoring Service (WGMS) and its predecessor organizations have been compiling and disseminating standardized data on glacier fluctuations. Thereto, the WGMS annually collects glacier data through its scientific collaboration network that is active in more than 30 countries. In close collaboration with the U.S. National Snow and Ice Data Center (NSIDC) and the Global Land Ice Measurements from Space (GLIMS) initiative, the WGMS runs the Global Terrestrial Network for Glaciers (GTN-G) in support of the United Nations Framework Convention on Climate Change (UNFCC). Global Glacier Changes: facts and figures. Website:
EPA – Climate Change
EPA’s purpose is to ensure that all Americans are protected from significant risks to human health and the environment where they live, learn and work. Website:
Intergovernmental Panel on Climate Change – IPCC
The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. Website:



  1. NASA Earth Observatory – 2009 Ends Warmest Decade on Record:
  2. Munich Re Website:
  3. – National Climate Assessment:
  4. NASA – Global Climate Change: Vital Signs of the Planet:
  5. Image Source: NASA – Global Climate Change: Vital Signs of the Planet: [Accessed: October 30, 2013]
  6. EPA – Causes of Climate Change:
  7. Image Source: [Accessed: May 25, 2013]
  8. Intergovernmental Panel on Climate Change (IPCC) – Fifth Assessment Report – Climate Change 2013: The Physical Science Basis:
  9. Image Source: IPCC Fourth Assessment Report: Climate Change 2007 – [Accessed: May 25, 2013]
  10. Image Source: [Accessed: May 25, 2013]