Climate Change and Global Warming Introduction

Author and Page information

by Anup Shah
This Page Last Updated Monday, March 05, 2012

This page: http://www.globalissues.org/article/233/climate-change-and-global-warming-introduction.
To print all information e.g. expanded side notes, shows alternative links, use the print version:

http://www.globalissues.org/print/article/233

This web page has the following sub-sections:

What is Global Warming and Climate Change?

What are the impacts of Global Warming?

Super-storms

Greenhouse gases and emissions resulting from human activity

Skepticism on Global Warming or That it can be human-induced

Bush Administration Accused of Silencing its own Climate Scientists

What is Global Warming and Climate Change?

Global warming and climate change refer to an increase in average global temperatures. Natural events and human activities are believed to be contributing to an increase in average global temperatures. This is caused primarily by increases in “greenhouse” gases such as Carbon Dioxide (CO₂).
A warming planet thus leads to a change in climate which can affect weather in various ways, as discussed further below.

What are the main indicators of Climate Change?

As explained by the US agency, the National Oceanic and Atmospheric Administration (NOAA), there are 7 indicators that would be expected to increase in a warming world (and they are), and 3 indicators would be expected to decrease (and they are):

Ten indicators for a warming world, Past Decade Warmest on Record According to Scientists in 48 Countries, NOAA, July 28, 2010

What is the Greenhouse Effect?

The term greenhouse is used in conjunction with the phenomenon known as the greenhouse effect.

Energy from the sun drives the earth’s weather and climate, and heats the earth’s surface;
In turn, the earth radiates energy back into space;
Some atmospheric gases (water vapor, carbon dioxide, and other gases) trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse;
These gases are therefore known as greenhouse gases;
The greenhouse effect is the rise in temperature on Earth as certain gases in the atmosphere trap energy.

Image source: Greenhouse Effect, Wikipedia(Link includes detailed explanation of the above image). Note, image above expresses energy exchanges in watts per square meter (W/m²)

Six main greenhouse gases are carbon dioxide (CO₂), methane (CH₄) (which is 20 times as potent a greenhouse gas as carbon dioxide) and nitrous oxide (N₂O), plus three fluorinated industrial gases: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF₆). Water vapor is also considered a greenhouse gas.

The Greenhouse effect is natural. What do we have to do with it?

Many of these greenhouse gases are actually life-enabling, for without them, heat would escape back into space and the Earth’s average temperature would be a lot colder.
However, if the greenhouse effect becomes stronger, then more heat gets trapped than needed, and the Earth might become less habitable for humans, plants and animals.
Carbon dioxide, though not the most potent of greenhouse gases, is the most significant one. Human activity has caused an imbalance in the natural cycle of the greenhouse effect and related processes. NASA’s Earth Observatory is worth quoting the effect human activity is having on the natural carbon cycle, for example:
In addition to the natural fluxes of carbon through the Earth system, anthropogenic (human) activities, particularly fossil fuel burning and deforestation, are also releasing carbon dioxide into the atmosphere.
When we mine coal and extract oil from the Earth’s crust, and then burn these fossil fuels for transportation, heating, cooking, electricity, and manufacturing, we are effectively moving carbon more rapidly into the atmosphere than is being removed naturally through the sedimentation of carbon, ultimately causing atmospheric carbon dioxide concentrations to increase.
Also, by clearing forests to support agriculture, we are transferring carbon from living biomass into the atmosphere (dry wood is about 50 percent carbon).
The result is that humans are adding ever-increasing amounts of extra carbon dioxide into the atmosphere. Because of this, atmospheric carbon dioxide concentrations are higher today than they have been over the last half-million years or longer.

— The Carbon Cycle; The Human Role, Earth Observatory, NASA

Another way of looking at this is with a simple analogy: consider salt and human health:

A small amount of salt is essential for human life;
Slightly more salt in our diet often makes food tastier;
Too much salt can be harmful to our health.

In a similar way, greenhouse gases are essential for our planet; the planet may be able to deal with slightly increased levels of such gases, but too much will affect the health of the whole planet.

Image source: NASA.(Note, values shown represent Carbon Gigatons being absorbed and released)

The other difference between the natural carbon cycle and human-induced climate change is that the latter is rapid. This means that ecosystems have less chance of adapting to the changes that will result and so the effects felt will be worse and more dramatic it things continue along the current trajectory.

The climate has always varied in the past. How is this any different?

Throughout Earth’s history the climate has varied, sometimes considerably. Past warming does not automatically mean that today’s warming is therefore also natural. Recent warming, has been shown to be due to human industrialization processes.
John Cook, writing the popular Skeptical Science blog summarizes the key indicators of a human finger print on climate change:

John Cook, 10 Indicators of a Human Fingerprint on Climate Change, Skeptical Science, July 30, 2010

This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric CO₂ has increased since the Industrial Revolution:

(Source: NOAA) via: Climate Change: How do we know? NASA, accessed October 27, 2009

The above covers hundreds of thousands of years and shows how atmospheric CO₂ levels have dramatically increased in recent years. If we “zoom” in on just the past 250 years, we see the following:

Global CO₂ emissions, 1751–2007, Carbon Dioxide Information Analysis Center (CDIAC), August 2010,DOI:10.3334/CDIAC/00001_V2010

NASA’s Goddard Institute of Space Studies (GISS) tracks atmospheric global temperature climate trends. As environmental engineer, D Kelly O’Day, writes on ProcessingTrends.com explains: “To facilitate assessments of long term trends, climatologists compare the mean for a base period with the annual mean. Differences between the annual mean and baseline mean are called anomalies. GISS uses the 1951 - 1980 period for their baseline period. They use the difference between the annual mean and the baseline mean to determine the global temperature anomaly for the year.”
O’Day produced a chart showing global temperature anomalies between 1800 and 2006 using data from NASA. I updated the chart he provided to include recently updated data up to 2011:

Sources: GISS Surface Temperature Analysis, NASA, accessed March 4, 2012; Global temperature, 1800-2006, ProcessTrends.com, accessed October 27, 2009

In the 1880 - 1935 period, the temperature anomaly was consistently negative. In contrast, the since 1980 the anomaly has been consistently positive. The 1917 temperature anomaly (-0.47oC) was the lowest year on record. Since 1917, global temperature has warmed, with the most recent years showing the highest anomalies of +0.6 oC in the past 120 years.
With slightly updated data from NASA’s GISS an animation shows how most parts of the world have experienced this warming, recently:

Global temperatures have warmed significantly since 1880, the beginning of what scientists call the “modern record.” At this time, the coverage provided by weather stations allowed for essentially global temperature data. As greenhouse gas emissions from energy production, industry and vehicles have increased, temperatures have climbed, most notably since the late 1970s. Source: NASA Finds 2011 Ninth Warmest Year on Record, NASA Goddard Institute for Space Studies, January 19, 2012

And, as Sir David Attenborough explains, natural variability alone does not explain recent temperature rise:

Sir David Attenborough: The Truth About Climate Change, October 22, 2006

As well as the links above, see also Skeptical Science, which, while examining the arguments of global warming skepticism, provides information on causes of anthropogenic global warming.

Doesn’t recent record cold weather disprove Global Warming?

In different parts of the world, there have been various weather events that at first thought would question global warming. For example, some regions have experienced extremely cold winters (sometimes record-breaking), while others have experienced heavy rain, etc.
The confusion that sometimes arises is the difference between climate change and weather patterns. Weather patterns describe short term events, while climate change is a longer process that affects the weather. A warming planet is actually consistent with increasing cold, increasing rain and other extremes, as an overall warmer planet changes weather patterns everywhere at all times of the year.
Deke Arndt, head of the Climate Monitoring Branch for the National Climatic Data Center in the US explains it with an analogy:
Climate kind of trains the boxer, but weather throws the punches. And what climate will do is help train weather to throw certain punches more often. We’ll see these as extreme precipitation events, extreme droughts.

— Deke Arndt, State of the Climate in 2009, NOAA, July 28, 2010

To get an idea of how looking at short term changes only can lead to a conclusion that global warming has stopped, or doesn’t exist, see Alden Griffith’s has global warming stopped?
(As an aside, those crying foul of global warming claims when going through extremely cold weather in Europe for example in 2010, later found their summers to be full of heat waves. The point here is that a specific short period such as a cold winter — or even a hot summer — is not proof alone that global warming has stopped (or increased); short term variability can mask longer term trends.)
This short video from TreeHugger and Skeptical Science’s John Cook explains how increasing temperatures can actually mean more snowfall — at least until it becomes too warm for significant snowfall to happen:

Record-Breaking Snow Doesn't Mean Global Warming Has Stopped, TreeHugger, April 14, 2011

Looking at 2010 as a whole year revealed a variety of extreme weather events. A panel of climate and weather experts ranked the top 10 global weather/climate events of 2010 which included heat waves to droughts to negative arctic oscillation (a climate pattern where cold Arctic air slides south while warmer air moves north, bringing snow storms and record cold temperatures to much of the Northern Hemisphere) show that a variety of weather events can occur as a result of changing climate:

Envionment ecological protection & Climate warming Biodiversity

Monday, June 11, 2012