Causes of global warming, explained
Aug 05, · Today’s climate change is driven by human activities. Scientists know that the warming climate is caused by human activities because: They understand how heat-trapping gases like carbon dioxide work in the atmosphere They know why those gases are increasing in the atmosphere. Jul 14, · Humans cause climate change. How do we know? Scientists agree that global warming is caused mainly by human activity. Specifically, the evidence shows that certain heat-trapping gases, such as carbon dioxide, are warming the world—and that we release those gases when we burn fossil fuels like coal, oil, and gas.
Sincethe average surface air temperature has risen 1. The steepest rise began in the s and continues today. We know this warming is happening because we have measurements of temperature from weather stations. In some places, recorded temperature measurements go back to the s. Estimates of temperature changes in the further past dause made from tree rings and ice cores.
Today, surface temperatures are monitored at thousands of places, over both land and oceans. An increase of 1. On average, Earth is only 7 to 9 degrees Fahrenheit warmer today than it was during the last ice age.
The recent increase in average temperature of only a couple changee is already leading to global changes in precipitation, snow and ice extent, and extreme weather, such as heavy rains, heat waves, and severe storms.
Today, Earth is warming at a much faster rate than it warmed over huamns 7, years since the last ice age. That means that Earth will get hotter over the course of a few decades rather than over a few thousand years. Human activities have increased the abundance of heat-trapping gases in the atmosphere.
This increase is mostly due to burning fossil fuels, such as coal, oil, and natural gas. Carbon dioxide has increased from a pre-industrial level of parts per million to more than parts per million today.
Most of the increase of carbon dioxide in cwuse atmosphere has occurred since the late s. It is true that Earth has cycled through many ice ages and warm periods in the past. Those past events have been driven by natural changes such as:. Scientists can measure these natural changes. The warm periods that regularly occurred between the ice ages of the past million years or so can be explained by natural changes, but measurements of those changes today cannot explain the current levels of warming that we are experiencing.
The rapid how do alligators see underwater we are experiencing today can only be explained by increasing amounts of carbon dioxide and other heat-trapping gases in the atmosphere.
The link between carbon dioxide in the atmosphere and rising global temperatures has been clear to scientists since the s. Measurements show that there is more carbon ddo in the atmosphere today than at any other time in the past 1 million years—that is, since the dawn of humankind. Human activities are causing Earth to heat up in ways that are different from warm periods in the past.
Earth is getting hotter. More Based on Science. For how to listen music on bluetooth headset from laptop evidence, look for multiple studies. Can science help people make decisions? What if scientific studies disagree?
Why do we still have cold weather if the earth is warming? Is climate change causing sea levels to rise? Are humans causing global warming? Is global warming contributing to extreme weather events? Published on: August 5,
A minor but very important component of the atmosphere, carbon dioxide is released through natural processes such as respiration and volcano eruptions and through human activities such as deforestation, land use changes, and burning fossil fuels. Humans have increased atmospheric CO 2 concentration by 47% since the Industrial Revolution began. How can human activities cause climate change? Our modern civilization is based on hydrocarbons: fuel and coal are the main sources of energy of our societies. Burning fuel and coal releases a great amount of carbon dioxide (CO 2) into the Earth's atmosphere. Jan 18, · One of the first things the IPCC concluded is that there are several greenhouse gases responsible for warming, and humans emit them in a variety of .
Scientists attribute the global warming trend observed since the mid th century to the human expansion of the "greenhouse effect" 1 — warming that results when the atmosphere traps heat radiating from Earth toward space. Certain gases in the atmosphere block heat from escaping. Long-lived gases that remain semi-permanently in the atmosphere and do not respond physically or chemically to changes in temperature are described as "forcing" climate change.
Gases, such as water vapor, which respond physically or chemically to changes in temperature are seen as "feedbacks. On Earth, human activities are changing the natural greenhouse. Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide CO 2. This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO 2.
To a lesser extent, the clearing of land for agriculture, industry, and other human activities has increased concentrations of greenhouse gases. The consequences of changing the natural atmospheric greenhouse are difficult to predict, but some effects seem likely:.
Outside of a greenhouse, higher atmospheric carbon dioxide CO 2 levels can have both positive and negative effects on crop yields. Some laboratory experiments suggest that elevated CO 2 levels can increase plant growth. However, other factors, such as changing temperatures, ozone, and water and nutrient constraints, may more than counteract anypotential increase in yield.
If optimal temperature ranges for some crops are exceeded, earlier possible gains in yield may be reduced or reversed altogether. Climate extremes, such as droughts, floods and extreme temperatures, can lead to crop losses and threaten the livelihoods of agricultural producers and the food security of communities worldwide.
Depending on the crop and ecosystem, weeds, pests, and fungi can also thrive under warmer temperatures, wetter climates, and increased CO 2 levels, and climate change will likely increase weeds and pests. Finally, although rising CO 2 can stimulate plant growth, research has shown that it can also reduce the nutritional value of most food crops by reducing the concentrations of protein and essential minerals in most plant species.
Climate change can cause new patterns of pests and diseases to emerge, affecting plants, animals and humans, and posing new risks for food security, food safety and human health.
In its Fifth Assessment Report, the Intergovernmental Panel on Climate Change, a group of 1, independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there's a more than 95 percent probability that human activities over the past 50 years have warmed our planet.
The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels from parts per million to parts per million in the last years. The panel also concluded there's a better than 95 percent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide have caused much of the observed increase in Earth's temperatures over the past 50 years. It's reasonable to assume that changes in the Sun's energy output would cause the climate to change, since the Sun is the fundamental source of energy that drives our climate system.
Indeed, studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity coupled with an increase in volcanic activity is thought to have helped trigger the Little Ice Age between approximately and , when Greenland cooled from to the s and glaciers advanced in the Alps.
But several lines of evidence show that current global warming cannot be explained by changes in energy from the Sun:. Not enough greenhouse effect: The planet Mars has a very thin atmosphere, nearly all carbon dioxide. Because of the low atmospheric pressure, and with little to no methane or water vapor to reinforce the weak greenhouse effect, Mars has a largely frozen surface that shows no evidence of life.
Too much greenhouse effect: The atmosphere of Venus, like Mars, is nearly all carbon dioxide. But Venus has about , times as much carbon dioxide in its atmosphere as Earth and about 19, times as much as Mars does , producing a runaway greenhouse effect and a surface temperature hot enough to melt lead.
The above graph compares global surface temperature changes red line and the Sun's energy that Earth receives yellow line in watts units of energy per square meter since Eleven-year averages are used to reduce the year-to-year natural noise in the data, making the underlying trends more obvious.
Over the same period, global temperature has risen markedly. It is therefore extremely unlikely that the Sun has caused the observed global temperature warming trend over the past half-century.
Images of Change. Explore a stunning gallery of before-and-after images of Earth from land and space that reveal our home planet in a state of flux. Climate Mobile Apps. Keep track of Earth's vital signs, see the planet in a state of flux and slow the pace of global warming with NASA's free mobile apps. Climate Time Machine. Travel through Earth's recent climate history and see how increasing carbon dioxide, global temperature and sea ice have changed over time.
Eyes on the Earth. Global Ice Viewer. Earth's ice cover is shrinking. See how climate change has affected glaciers, sea ice, and continental ice sheets.