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Climate Change


The Driving Force Of Climate Change Is Population Growth

Between 1960 and 1999, Earth's population doubled from three billion to six billion people. When population growth is coupled with shortsighted planning and excessive consumption of resources, problems multiply.


Human pressure on the environment is a product of three factors: population, consumption, and technology.   


Population is the total number of people, consumption is the amount of resources each person consumes, and technology is how these resources are used and how much waste is produced for each unit of consumption.


We have transformed approximately half of The Earth's surface for our own uses, with  widespread impacts on the planet's forests, oceans, freshwater, and atmosphere.

Climate includes patterns of temperature, precipitation, humidity, wind and seasons. "Climate change" affects more than just a change in the weather, it refers to seasonal changes over a long period of time. These climate patterns play a fundamental role in shaping natural ecosystems, and the human economies and cultures that depend on them.

What is climate forcing and how does climate forcing relate to climatic variability and change?

Climate forcing refers to specific phenomena that directly influence changes in climatic dynamics. Forces that influence climatic change can be broken down into those beyond the Earth's environmental system (extraterrestrial) and those that relate to internal forces (terrestrial).

Solar variability (sunspots 11, 22 yrs)
Obliquity (tilt on axis~41,000 yrs change)
Precession (wobble on axis due to gravity of sun and moon in 23,000 yr. cycle)
Eccentricity (96,000 yr. change)

Continental Processes (105 yrs. on up)
Mass and composition of atmosphere
Volcanic activity and strato aerosols
Thermohaline circulation
Human influences such as land use and combustion of fossil fuels


What factors are key to measuring climate change?

Temperature is the primary measure of climate and can be measured or reconstructed for the Earth's surface, and sea surface temperature (SST).

Precipitation offers another indicator of relative climate variation and may include humidity or water balance.

Biomass and vegetation patterns may be discerned in a variety of ways and provide evidence of how ecosystems change to adapt to climate change.

Sea Level measurements reflect changes in shoreline and usually relate to the degree of ice coverage in high latitudes and elevations.

Solar Activity can influence climate, primarily through changes in the intensity of solar radiation.

Volcanic Eruptions, like solar radiation, can alter climate due to the aerosols that are emitted into the atmosphere and alter climate patterns.

Chemical composition of air or water can be measured by tracking levels of greenhouse gases such as carbon dioxide and methane, and measuring ratios of oxygen isotopes. Research indicates a strong correlation between the percent of carbon dioxide in the atmosphere and the Earth's mean temperature.

The earth’s climate is predicted to change through the buildup of greenhouse gases – primarily water vapor, carbon dioxide, methane, and nitrous oxide. The heat-trapping property of these gases is undisputed. Although uncertainty exists about exactly how earth’s climate responds to these gases, global temperatures are rising.



Global climate change is a change in the long-term weather patterns that characterize the regions of the world. The term "weather" refers to the short-term (daily) changes in temperature, wind, and/or precipitation of a region.

What is the difference between Weather and Climate?

Weather is the state of atmosphere-ocean-land conditions (hot/cold, wet/dry, calm/stormy, sunny/cloudy) that exist over relatively short periods like hours or days. Weather includes the passing of a thunderstorm, hurricane, or blizzard, a persistent heatwave, a cold snap, a drought. Weather variability and extreme events may respond unpredictably in response to climate change.

Climate is weather patterns over a month, a season, a decade, a century from now or in past time periods. More technically climate is defined as the weather conditions resulting from the mean state of the atmosphere-ocean-land system, often described in terms of "climate normals"
or average weather conditions.

The greenhouse effect is a natural occurrence that maintains Earth's average temperature at approximately 60 degrees Fahrenheit. The greenhouse effect is a necessary phenomenon that keeps all Earth's heat from escaping to the outer atmosphere. Without the greenhouse effect, temperatures on Earth would be much lower than they are now, and the existence of life on this planet would not be possible. However, too many greenhouse gases in Earth's atmosphere could increase the greenhouse effect. 


This could result in an increase in mean global temperatures as well as changes in precipitation patterns. When weather patterns for an area change in one direction over long periods of time, they can result in a net climate change for that area. The key concept in climate change is time. Natural changes in climate usually occur over; that is to say they occur over such long periods of time that they are often not noticed within several human lifetimes. This gradual nature of the changes in climate enables the plants, animals, and Microorganisms on earth to evolve and adapt to the new temperatures, precipitation patterns, etc. The real threat of climate change lies in how rapidly the change occurs. Increasing concentrations of greenhouse gases are likely to accelerate the rate of climate change. 

Because so many systems are tied to climate, a change in climate can affect many related aspects of where and how people, plants and animals live, such as food production, availability and use of water, and health risks.

The Earth's climate has changed throughout history. From glacial periods (or "ice ages") where ice covered significant portions of the Earth to interglacial periods where ice retreated to the poles or melted entirely - the climate has continuously changed. Scientists have been able to piece together a picture of the Earth's climate dating back decades to millions of years ago by analyzing a number of surrogate, or "proxy," measures of climate such as ice cores, boreholes, tree rings, glacier lengths, pollen remains, and ocean sediments, and by studying changes in the Earth's orbit around the sun.

Temperatures over the last 4.6 billion years

The term Global Warming refers to the observation that the atmosphere near the Earth's surface is warming. This warming is one of many kinds of climate change that the Earth has gone through in the past and will continue to go through in the future. It is reasonable to expect that the Earth should warm as the amount of greenhouse gases in the atmosphere increases. It is known for certain that atmospheric concentrations of greenhouse gases are rising dramatically due to human activity. It is less well known exactly how the increases in these greenhouse gases factor in the observed changes of the Earth's climate and global temperatures

Human beings can contribute to global warming and climate change by polluting and cutting down rainforests, but humans can not control the climate or change it. The climate system is very complex and has many variables and components. Human beings do not control all the variables and components or the Planet Earth.

Any organization or person that is saying things like "we can solve the climate crisis" or "we can stop global warming" are making statements that are just "Advertising Slogans"  impossible to accomplish. 

To actually "stop global warming" or "solve the climate crisis" human beings would have the ability to control the following to name a few:

  • The Sun 

  • Volcanic Activity

  • The Weather

  • The Atmosphere

  • All Human Activities

  • The Oceans

No matter how aggressively heat-trapping emissions are reduced, some amount of climate change and resulting impacts will continue. Consequently, there is a need for adaptation and mitigation. 

“Adaptation” – improving our ability to cope with or avoid harmful impacts or taking advantage of newly favorable conditions

Mitigation is defined as -to lessen in force or intensity, as wrath, grief, harshness, or pain; moderate- to make less severe. At best human beings can slightly modify climate change. 

“Mitigation” – reducing the amount of climate change, for example, by reducing heat-trapping emissions or increasing their removal from the atmosphere

We should try to be the best protectors of the planet as much as we are capable and adapt to and prepare for the changes in the Earth's Climate that are inevitable.

If we stop all greenhouse gas emissions, will global climate change stop?

Industrial activity has already pumped billions of tons of greenhouse gases into the atmosphere, and we have yet to see the full effect of warming from those gases. A great deal of excess energy imbalance is stored in the ocean and will be released gradually over time, continuing to warm the planet.

In other words, some degree of climate change is irreversible. Scientists call this the "committed warming," and estimate that the Earth would continue to warm about 1 degree Fahrenheit (.6 degrees Celsius) even if greenhouse gas levels in the atmosphere stopped growing immediately. That is, if all human greenhouse gas emissions stopped tomorrow, the Earth would still warm for at least a half-century.

Climate History

Over the last 400,000 years the Earth's climate has been unstable, with very significant temperature changes, going from a warm climate to an ice age in as rapidly as a few decades. These rapid changes suggest that climate may be quite sensitive to internal or external climate forcings and feedbacks. As can be seen from the blue curve, temperatures have been less variable during the last 10 000 years. Based on the incomplete evidence available, it is unlikely that global mean temperatures have varied by more than 1°C in a century during this period. The information presented on this graph indicates a strong correlation between carbon dioxide content in the atmosphere and temperature. A possible scenario: anthropogenic emissions of GHGs could bring the climate to a state where it reverts to the highly unstable climate of the pre-ice age period. Rather than a linear evolution, the climate follows a non-linear path with sudden and dramatic surprises when GHG levels reach an as-yet unknown trigger point.

Volcano emmissions

The more than 500 active volcanoes erupting around the world affect the Earth's atmosphere and global climate. As volcanoes erupt, they blast large clouds of gases, particles, water vapor, and aerosols into the atmosphere.


Causes of Change Prior to the Industrial Era (pre-1780)

Known causes, “drivers” or “forcings” of past climate change include:

  • Changes in the Earth's orbit: Changes in the shape of the Earth's orbit  as well as the Earth's tilt and precession affect the amount of sunlight received on the Earth's surface. These orbital processes -- which function in cycles of 100,000 (eccentricity), 41,000 (tilt), and 19,000 to 23,000 (precession) years -- are thought to be the most significant drivers of ice ages according to the theory of ,Mulitin Milankovitch a Serbian mathematician (1879-1958). 

  • Changes in the sun's intensity: Changes occurring within (or inside) the sun can affect the intensity of the sunlight that reaches the Earth's surface. The intensity of the sunlight can cause either warming (for stronger solar intensity) or cooling (for weaker solar intensity). According to NASA research, reduced solar activity from the 1400s to the 1700s was likely a key factor in the “Little Ice Age” which resulted in a slight cooling of North America, Europe and probably other areas around the globe.

  • Volcanic eruptions: Volcanoes can affect the climate because they can emit aerosols and carbon dioxide into the atmosphere.

    • Aerosol emissions: Volcanic aerosols tend to block sunlight and contribute to short term cooling. Aerosols do not produce long-term change because they leave the atmosphere not long after they are emitted. According to the United States Geological Survey (USGS), the eruption of the Tambora Volcano in Indonesia in 1815 lowered global temperatures by as much as 5ºF and historical accounts in New England describe 1816 as “the year without a summer.”

    • Carbon dioxide emissions: Volcanoes also emit carbon dioxide (CO2), a greenhouse gas, which has a warming effect. For about two-thirds of the last 400 million years, geologic evidence suggests CO2 levels and temperatures were considerably higher than present. One theory is that volcanic eruptions from rapid sea floor spreading elevated CO2 concentrations, enhancing the greenhouse effect and raising temperatures. However, the evidence for this theory is not conclusive and there are alternative explanations for historic CO2 levels  While volcanoes may have raised pre-historic CO2 levels and temperatures, according to the USGS Volcano Hazards Program, human activities now emit 150 times as much CO2 as volcanoes (whose emissions are relatively modest compared to some earlier times).

These climate change “drivers” often trigger additional changes or “feedbacks” within the climate system that can amplify or dampen the climate's initial response to them (whether the response is warming or cooling). For example:

  • Changes in greenhouse gas concentrations: The heating or cooling of the Earth's surface can cause changes in greenhouse gas concentrations. For example, when global temperatures become warmer, carbon dioxide is released from the oceans. When changes in the Earth's orbit trigger a warm (or interglacial) period, increasing concentrations of carbon dioxide may amplify the warming by enhancing the greenhouse effect. When temperatures become cooler, CO2 enters the ocean and contributes to additional cooling. During at least the last 650,000 years, CO2 levels have tended to track the glacial cycles . That is, during warm interglacial periods, CO2 levels have been high and during cool glacial periods, CO2 levels have been low

Changes in ocean currents: The heating or cooling of the Earth's surface can cause changes in ocean currents. Because ocean currents play a significant role in distributing heat around the Earth, changes in these currents can bring about significant changes in climate from region to region.

The Last 2,000 Years

During the last 2,000 years, the climate has been relatively stable. Scientists have identified three departures from this stability, known as the Medieval Climate Anomaly (also referred to as the Medieval Warm Period), the Little Ice Age and the Industrial Era:

  • The Medieval Climate Anomaly: Between roughly 900 and 1300 AD, evidence suggests Europe, Greenland and Asia experienced relative warmth. While historical accounts and other evidence document the warmth that occurred in some regions, the geographical extent, magnitude and timing of the warmth during this period is uncertain . The American West experienced very dry conditions around this time.

  • The Little Ice Age: A wide variety of evidence supports the global existence of a "Little Ice Age" (this was not a true "ice age" since major ice sheets did not develop) between about 1500 and 1850 . Average temperatures were possibly up to 2ºF colder than today, but varied by region.

  • The Industrial Era: An additional warm period has emerged in the last 100 years, coinciding with substantially increasing emissions of greenhouse gases from human activities 

Prior to the Industrial Era,  the Medieval Climate Anomaly and Little Ice Age had defined the upper and lower boundaries of the climate's recent natural variability and are a reflection of changes in climate drivers (the sun's variability and volcanic activity) and the climate's internal variability (referring to random changes in the circulation of the atmosphere and oceans).



The ice ages

Precambrian time included almost all of Earth's first 4 billion years. The crust, the atmosphere, and the oceans were formed, and the simplest kinds of life appeared. 

Throughout the history of Earth, the climate has changed many times. Between 800 million and 600 million years ago, during a time called the Precambrian, Earth experienced several extreme climate changes called ice ages or glacial epochs. The climate grew so cold that some scientists believe Earth nearly or completely froze several times. The theory that the entire Earth froze is sometimes called the snowball Earth. Geologists estimate that Earth experienced up to four such periods of alternate freezing and thawing.
Most of the time, Earth has been largely ice free. Brief ice ages occurred about 450 million years ago and again about 250 million years ago. In the last few million years, however, Earth's climate began to cool. Glaciers began forming in Antarctica about 35 million years ago, but the climate there was warm enough for trees to grow until about 5 million years ago. By about 2 million years ago, at the beginning of a time called the Pleistocene Epoch, ice had accumulated on other continents as well.

Numerous separate ice advances, periods when ice sheets covered vast areas, occurred during the Pleistocene Ice Age. The advances alternated with periods when the climate was warmer and the ice melted. Geologists analyzing sediment deposits from the North Atlantic Ocean determined that there were at least 20 advances and retreats of ice sheets in the past 2 million years. At least four ice advances were big enough to extend over much of Europe, cover most of Canada, and reach deep into the United States.

The most recent advance of ice began about 70,000 years ago and reached its farthest extent about 18,000 years ago. The vast glaciers and sheets of ice scoured out the basins of the Great Lakes and blocked rivers, completely changing the courses of the Mississippi, Missouri, and Ohio rivers. So much water was trapped in the form of ice that sea level around Earth dropped as much as 390 feet (120 meters), exposing parts of the present ocean floor.

The most recent ice advance ended about 11,500 years ago. Most scientists believe that Earth is currently in an interglacial period, and another ice advance will follow.

Why ice ages occur

Scientists do not fully understand why Earth has ice ages. Most believe that tiny changes in Earth's orbit and axis due to the gravitational pull of other planets play a part. These changes alter the amount of energy received from the sun.

Many scientists also believe that variations in the amount of carbon dioxide in the atmosphere are responsible for long-term changes in the climate. Carbon dioxide, a "greenhouse gas," traps heat from the sun and warms Earth's atmosphere. Most of Earth's carbon dioxide is locked in carbonate rocks, such as limestone and dolomite. Earth's climate today would be much warmer if the carbon dioxide trapped in limestone were released into the atmosphere.

When mountains rich in silicate minerals wear down through weathering and erosion, calcium and magnesium erode from the rocks. These elements are carried to the sea by water. There, living organisms absorb the chemicals and use them to make protective carbonate shells. The organisms eventually die and sink to the bottom to form limestone deposits. This process, called the carbonate-silicate cycle, removes carbon dioxide from the atmosphere. With less carbon dioxide in the atmosphere to trap heat from the sun, Earth's climate may cool enough to cause an ice age.

Limestone and dolomite deposits exposed to weathering and erosion return carbon dioxide to the atmosphere and contribute to global warming. In addition, some limestone on the ocean floor can be carried down into Earth's mantle by subduction. Beneath the crust, the limestone breaks down into magma under heat and pressure. The carbon dioxide in the limestone can then return to the atmosphere during volcanic eruptions.

Scientists theorize that volcanoes continued to emit carbon dioxide into the atmosphere during the Precambrian ice ages. Eventually, the carbon dioxide warmed Earth through the greenhouse effect, causing the ice to melt rapidly.

Climate and Health

Climate can have a profound influence on human health both directly and indirectly.  Some direct effects include deaths and illnesses related to excessive heat or cold exposure.  Indirect effects of climate on health may involve respiratory disorders due to air pollution, including spores and pollens.  Incidences of waterborne diseases, such as cholera, as well as food productivity and its relation to nutrition are other indirect effects of climate on health. 

Human health is also indirectly affected by climate due to its influence on the abundance and geographic distribution of disease vectors, such as mosquitoes and rodents.  Several studies suggest projected climate changes may result in expanded geographic ranges for many mosquito-borne diseases. 

Mosquitoes can  transmit many viruses, over 100 of which are known to infect humans. These include malaria, dengue fever, yellow fever, and severe and sometimes fatal encephalitis and haemorrhagic fever.



Sources: NASA Oceanography, EPA, UNEP, Environment Canada, CDC,U.S. Fish & Wildlife Service