Emissions from the widespread burning of fossil fuels since the start of the Industrial Revolution have increased the concentration of greenhouse gases in the atmosphere. Because these gases can remain in the atmosphere for hundreds of years before being removed by natural processes, their warming influence is projected to persist into the next century. Jump to “The burning of fossil fuels has increased greenhouse gases”
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Culture, Climate Science & Education
What You Need to Know About Principle 7: Humans Affect Climate
We have known about the greenhouse effect for a long time. It has been described for over 150 years, in fact, and for over a century we have been calculating the potential for human activities to increase the temperature of the Earth through greenhouse gas emissions. And we have known about possible consequences: In 1958, the National Academy of Sciences published a booklet titled “Planet Earth: The Mystery with 100,000 Clues,” which contained this paragraph:
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Most of the increase in global average temperatures is human caused
The overwhelming consensus of scientific studies on climate indicates that most of the observed increase in global average temperatures since the latter part of the 20th century is very likely due to human activities, primarily from increases in greenhouse gas concentrations resulting from the burning of fossil fuels.
While there is public debate on some TV stations and in some newspapers about the cause of recent climate change, there is generally no debate about the cause of climate change among climate scientists or the peer reviewed literature.
What is this? click the image to enlarge and find out.
click the image to enlarge
The graphs below will tell you a great deal about the cause of global warming. To navigate through the graphs, scroll down until you see the down arrow and click it. Take a look also at the feature article.
The burning of fossil fuels has increased greenhouse gases
Emissions from the widespread burning of fossil fuels since the start of the Industrial Revolution have increased the concentration of greenhouse gases in the atmosphere. Because these gases can remain in the atmosphere for hundreds of years before being removed by natural processes, their warming influence is projected to persist into the next century.
Fossil fuels are very concentrated forms of transformed solar energy. It’s been estimated that one gallon of gasoline equals 98 tons of biomass. It is important to acknowledge that extremely powerful and portable forms of fossil fuel energy have been liberating in many respects, allowing machines to do work that would otherwise be done by human or animal muscle-power. The world has changed tremendously, socially, economically and environmentally due to fossil fuels. Read more…
How much CO2 do you emit?
The images immediately below allow you to visualize better your carbon output. One slide shows how much carbon different kinds of light bulbs emit in a day (on average). Another shows how much carbon is released when you burn a gallon of gasoline. Another two show the average per capita (per person) carbon output for 4 countries and the world.
Visualizing Your Carbon Output
You can calculate your own personal carbon footprint by clicking here.
Human activities have altered global climate patterns
Human activities have affected the land, oceans, and atmosphere, and these changes have altered global climate patterns. Burning fossil fuels, releasing chemicals into the atmosphere, reducing the amount of forest cover, and rapid expansion of farming, development, and industrial activities are releasing carbon dioxide into the atmosphere and changing the balance of the climate system.
Human-caused global warming has caused changes in many physical and biological systems
Growing evidence shows that changes in many physical and biological systems are linked to human-caused global warming. Some changes resulting from human activities, like the production of greenhouse gases, have decreased the ability of the environment to support some species and have substantially reduced biodiversity and ecological resilience.
In the United States the Clean Air Act and the Clean Water Act have been used to monitor and regulate specific forms of pollution, helping to minimize the impacts of acid rain and severe water pollution from industrial and municipal sources. Read more…
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What's Happening to Arctic Sea Ice?
The chart below shows Arctic sea ice minimums since 1979.
The heavy black line shows the average for the period between 1981 and 2010.
For good summaries of how human-caused global warming has caused changes in physical and biological systems and human communities, click through some of the different sectors described in the National Climate Assessment:
Or view the impacts to the Southeast region:
There will be both positive and negative impacts from global climate change but negative impacts are likely to be much greater than positive
Scientists and economists predict that there will be both positive and negative impacts from global climate change. If warming exceeds 2 to 3°C (3.6 to 5.4°F) over the next century, the consequences of the negative impacts are likely to be much greater than the consequences of the positive impacts.
Life is adaptive and human beings can be resilient to challenges presented them. While stopping global warming completely isn’t possible, there is much we can do to minimize the impacts and prepare our communities, locally and globally, to be able to withstand the known and unknown impacts ahead.
For good summaries of Adaptation strategies, visit the National Climate Assessment:
Hurricanes and Climate Change
As the climate continues to warm, the frequency of intense hurricanes in the North Atlantic is projected to rise
Sandy. Katrina. Andrew. Ike.
Wilma. Ivan. Charley. Irene.
For coastal communities, the social, economic, and physical scars left behind by major hurricanes can be devastating.
While hurricanes are a natural part of our climate system, recent research suggests that their destructive power, or intensity, has been growing since the 1970s, particularly in the North Atlantic region.
A growing number of people and structures are at risk from the increasingly destructive potential of hurricanes, a trend exacerbated by sea level rise and rapid population growth.
The aftermath of Hurricane Ike in Gilchrist, Texas, in 2008.
Factors that increase the destructive potential of hurricanes
The oceans have taken in nearly all of the excess energy created by global warming, absorbing 93 percent of the increase in the planet’s energy inventory from 1971-2010.
In some ocean basins, hurricane intensification has been linked to rising ocean temperatures. Since 1970, tropical ocean sea surface temperatures worldwide have warmed by about an average of 0.5°C. Warming in the North Atlantic basin has been more rapid—about 0.7°C since the 1980s.
Sea levels are also rising in response as the oceans warm and seawater expands. This expansion, combined with the melting of land-based ice, has caused global average sea level to rise by roughly 8 inches since 1880—a trend that is expected to accelerate over coming decades.
Higher sea levels give coastal storm surges a higher starting point when major storms approach and pile water up along the shore. The resulting storm surge reaches higher and penetrates further inland in low-lying areas. The risk is even greater if storms make landfall during high tides.
Roads and other crucial infrastructure face growing risks from storm surges.
Roughly a third of the US population—more than 100 million people—lives in coastal counties. US coastal county populations are also growing much denser than non-coastal counties. Between 1980 and 2008 coastal counties increased population density by 28 percent (excluding Alaska). In non-coastal counties, population density hardly changed over the same period.
By concentrating ourselves along the coasts, we have increasingly exposed our communities and homes to powerful storms. As a result of coastal development, storms are exacting rising financial tolls.
Observed trends in hurricanes
The number and strength of storms is highly variable from year to year, which makes it challenging to detect trends in the frequency or intensity of hurricanes over time.
Storm counts and strength measurements were also less consistent prior to the 1970s when satellite observations began, further complicating the study of long-term trends.
To help address these challenges, scientists run hurricane models calibrated with observations over the historical period to project future trends and understand their major contributing factors.
Recent research in this area suggests that hurricanes in the North Atlantic region have been intensifying over the past 40 years.
Since the mid-1970s, the number of hurricanes that reach Categories 4 and 5 in strength—that is, the two strongest classifications—has roughly doubled.
Measures of the potential destructiveness of hurricanes (a measure of the power of a hurricane over its entire lifetime) also show a doubling during this time period. Indices for hurricane activity based on storm surge data from tide gauges further indicate an increase in intensity.
Hurricanes in the western North Pacific and the northern Indian oceans—known as typhoons and cyclones, respectively—are also intensifying, though the signal is not as strong as for the North Atlantic. Whether hurricanes are intensifying in other regions is less clear, though other recent evidence suggests that the trend toward more intense hurricanes may extend globally.
There has been little change, however, in the frequency of hurricanes globally. Roughly 90 hurricanes occur each year around the world, with by far the greatest number occurring in the largest ocean basin on Earth–the Pacific.
To further address the challenges of detecting long-term trends, scientists also study the core factors that intensify or weaken hurricanes, including the interplay between human-driven climate change and natural factors.
Percent of Atlantic hurricanes each year from 1970 to 2012 that reached categories 3, 4, and 5. Annual data (light blue) and 5-year running average (dark blue).
Rising ocean temperatures fuel stronger North Atlantic hurricanes
Warm ocean temperatures are one of the key factors that strengthen hurricane development when overall conditions are conducive for their formation and growth.
Hurricanes require high humidity, relatively constant winds at different altitudes, and can occur when surface ocean temperatures exceed about 79°F (26°C). The rising of warm, moist air from the ocean helps to power the storm.
In order to build up and intensify, hurricanes require warm ocean temperatures, moist air, and low vertical wind shear (i.e. no strong change in wind speed or direction between two different altitudes).
Because of this link between warm oceans and hurricane behavior, warming of the surface ocean can increase the intensity of hurricanes, with the stronger ones getting the biggest boost. While hurricanes that make landfall are comparatively rare, they are responsible for vast economic damage in the United States.
Two other factors may also be contributing to the rising intensities of hurricanes. First, warm air holds more water vapor than cold air—and the rising air temperatures since the 1970s have caused the atmospheric water vapor content to rise as well. This increased moisture provides additional fuel for hurricanes. Indeed, hurricanes indicate a trend toward producing more torrential downpours, both in the historical record and in climate models that project future conditions.
Second, as ocean temperatures rise, there is also less cold, subsurface ocean water to serve as a braking mechanism for hurricanes. When strong storm winds churn up cold subsurface water, the cooler waters can serve to weaken the storm. But if deeper waters become too warm, this natural braking mechanism weakens. Hurricane Katrina, for example, intensified significantly when it hit deep pools of warm water in the Gulf of Mexico.
The largest Atlantic hurricane on record, Hurricane Sandy reached over 1000 miles in diameter and made landfall in the U.S. on October 29, 2012.
The role of natural cycles in hurricanes
The oceans experience a variety of natural circulation patterns, or oscillations, that influence the distribution of warm and cold water in the upper ocean. These naturally occurring oscillations affect ocean conditions on timescales ranging from just a few years to several decades and are known to affect the intensity of hurricanes.
During the warm, or El Niño, phase of the El Niño Southern Oscillation (ENSO), for example, hurricanes are less likely to make landfall in eastern Australia and Atlantic hurricanes tend to be suppressed. However, El Niño conditions can boost typhoon risks in parts of Asia.
The presence of these natural oscillations can mask or enhance the potential influence of human-caused warming on hurricane activity.
The aftermath of Hurricane Sandy in Mantaloking, New Jersey.
What the future holds
As the climate continues to warm, the frequency of intense hurricanes in the North Atlantic is projected to rise while the overall number of hurricanes globally is expected to either decline or remain unchanged.
The projected increase in intense hurricanes is substantial—a doubling or more in the frequency of category 4 and 5 storms by the end of the century—with the western North Atlantic experiencing the largest increase. With continued warming, sea level is likely to rise by one to four feet globally by the end of the century, enabling the powerful surge associated with hurricanes to penetrate further inland than today.
Given the loss of life and the huge costs of rebuilding after hurricanes, it is essential to do whatever we can to avoid dangerous warming and protect coastal communities for ourselves and our children.
Misconceptions about this Principle
Humans are too insignificant to affect global climate
The misconception or myth goes something like this: “Humans are not capable of impacting forces as large as the climate. The climate system is simply too vast, too complicated.”
Humans can change the atmosphere and the atmosphere has a profound influence over the climate.
The science says: yes, it’s easy to feel insignificant relative to weather events like hurricanes and floods, and indeed as individuals we are. But through our collective pollution, we are capable of changing the atmosphere. Just look at the photo of a not-uncommon day in Bejing, China at left. That’s not fog, it is pollution from burning coal and other fossil fuels. And when you change the atmosphere in the ways we have been changing it, you change the climate. Read more…