What Is Climate Change?

Climate change refers to long-term shifts in temperatures and weather patterns. It is generally defined as a significant
variation of average weather conditions—say, conditions becoming warmer, wetter, or drier—over several decades or
more. It’s the longer-term trend that differentiates climate change from natural weather variability.

Record floods. Raging storms. Deadly heat. Climate change manifests itself in myriad ways and is experienced by every
living being, although not equally. Throughout the world, the economically disadvantaged and people of color—those
who have contributed the very least to the root causes of climate change—are the most likely to suffer from its worst
impacts. Here are the basics on what causes climate change, how it’s affecting the planet and its people, and what we
can do about it.

Despite what climate deniers and fossil fuel lackeys claim—for instance, that the science on global warming is “far from
settled”—there’s nothing to debate: Climate change is a reality. In the words of the Intergovernmental Panel on Climate
Change (IPCC), the foremost international scientific body for the assessment of the phenomenon, “[w]arming of the
climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to
millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has
risen.”

But you don’t have to be a climate scientist to understand how the world has already changed. Our last decade—2010 to
2019—was hotter than any other decade in at least the past 1,300 years. Second place goes to the decade before it:
2000 to 2009. And the first year of the new decade, 2020, is tied with 2016 for the hottest individual year ever
recorded. With this increased heat, of course, have come more frequent and more intense weather-related disasters.
The first half of 2021 was marked by record heat, drought, and wildfires in the western United States and Canada and
by record rainfall and flooding in Europe. And without immediate climate action, these records won’t be records for long:
They’ll be broken next year, or shortly thereafter. “The science is clear,” writes Vijay Limaye, NRDC scientist. “These
dangerous effects of climate change will worsen each year that we fail to curb the pollution that is destabilizing our
planet.”

What is Global Warming?

Global warming—the recent rise in the global average temperature near the earth’s surface—is just one aspect of
climate change.

How Is Climate Change Measured Over Time?

Climate refers to the general weather conditions of a place as measured over many years. In the United States, for
example, Maine’s climate is cold and snowy in winter while South Florida’s is tropical year-round.

Earth-orbiting satellites, remote meteorological stations, and ocean buoys are used to monitor present-day weather and
climate, but it’s paleoclimatology data from natural sources like ice cores, tree rings, corals, and ocean and lake
sediments that have enabled scientists to extend the earth’s climatic records back millions of years. These records provide
a comprehensive look at the long-term changes in the earth’s atmosphere, oceans, land surfaces, and cryosphere (frozen
water systems). Scientists then feed this data into sophisticated climate models that are able to predict future climate
trends with impressive accuracy.

Causes of climate change

When energy from the sun is reflected off the earth and back into space (mostly by clouds and ice), or when the earth’s
atmosphere releases energy, the planet cools. When the earth absorbs the sun’s energy, or when atmospheric gases
prevent heat released by the earth from radiating into space (the greenhouse effect), the planet warms. A variety of
factors, both natural and human, can influence the earth’s climate system.
A. Nature
Such shifts can be natural, due to changes in the sun’s activity or large volcanic eruptions. The earth has gone through warming
and cooling phases in the past, long before humans were around. Forces that can contribute to climate change include the sun’s
intensity, volcanic eruptions, and changes in naturally occurring greenhouse gas concentrations. But records indicate that today’s
climatic warming—particularly that which has occurred since the mid-20th century—is happening at a much faster rate than ever
before, and it can’t be explained by natural causes alone. According to NASA, “[t]hese natural causes are still in play today, but
their influence is too small or they occur too slowly to explain the rapid warming seen in recent decades

B. Human
Humans—more specifically, the greenhouse gas (GHG) emissions that human activity generates—are the leading cause of the
earth’s rapidly changing climate today. Greenhouse gases play an important role in keeping the planet warm enough to inhabit.
But the amount of these gases in our atmosphere has skyrocketed in recent decades. According to the U.S. Environmental
Protection Agency, our current concentrations of carbon dioxide, methane, and nitrous oxide “are unprecedented compared with
the past 800,000 years.” Indeed, the atmosphere’s share of carbon dioxide—the planet’s chief climate change contributor—has
risen by 46 percent since preindustrial times.

But since the 1800s, human activities have been the main driver of climate change, primarily due to the burning of fossil fuels
like coal, oil and gas.

The burning of fossil fuels like coal, oil, and gas for electricity, heat, and transportation is the primary source of human-generated
emissions. A second major source is deforestation, which releases sequestered (or stored) carbon into the air. It’s estimated that
logging, clearcutting, fires, and other forms of forest degradation release an average of 8.1 billion metric tons of carbon dioxide
per year, accounting for more than 20 percent of all global CO2 emissions. Other human activities that generate air pollution
include fertilizer use (a primary source of nitrous oxide emissions), livestock production (cattle, buffalo, sheep, and goats are
major methane emitters), and certain industrial processes that release fluorinated gases. Activities like agriculture and road
construction can also change the reflectivity of the earth’s surface, leading to local warming or cooling.

The main greenhouse gases that are causing climate change include carbon dioxide and methane. These come from using
gasoline for driving a car or coal for heating a building, for example. Clearing land and cutting down forests can also release
carbon dioxide. Agriculture, oil and gas operations are major sources of methane emissions. Energy, industry, transport,
buildings, agriculture and land use are among the main sectors causing greenhouse gases.

Though our planet’s forests and oceans absorb greenhouse gases from the atmosphere through photosynthesis and other
processes, these natural carbon sinks can’t keep up with our rising emissions. The resulting buildup of greenhouse gases is
causing alarmingly fast warming worldwide. It’s estimated that the earth’s average temperature rose by about 1 degree
Fahrenheit during the 20th century. If that doesn’t sound like much, consider this: When the last ice age ended and the
northeastern United States was covered by more than 3,000 feet of ice, average temperatures were just 5 to 9 degrees cooler
than they are now.

Humans are responsible for virtually all global heating over the last 200 years. Human activities like the ones mentioned above
are causing greenhouse gases that are warming the world faster than at any time in at least the last two thousand years.

The average temperature of the Earth’s surface is now about 1.1°C warmer than it was in the late 1800s (before the industrial
revolution) and warmer than at any time in the last 100,000 years. The last decade (2011-2020) was the warmest on record,
and each of the last four decades has been warmer than any previous decade since 1850.

Many people think climate change mainly means warmer temperatures. But temperature rise is only the beginning of the story.
Because the Earth is a system, where everything is connected, changes in one area can influence changes in all others.

The consequences of climate change now include, among others, intense droughts, water scarcity, severe fires, rising sea levels,
flooding, melting polar ice, catastrophic storms and declining biodiversity.

The emissions that cause climate change come from every part of the world and affect everyone, but some countries produce
much more than others.The seven biggest emitters alone (China, the United States of America, India, the European Union,
Indonesia, the Russian Federation, and Brazil) accounted for about half of all global greenhouse gas emissions in 2020.
Effect of climate change
Climate change can affect our health, ability to grow food, housing, safety and work. Some of us are already more vulnerable to
climate impacts, such as people living in small island nations and other developing countries. Conditions like sea-level rise and
saltwater intrusion have advanced to the point where whole communities have had to relocate, and protracted droughts are
putting people at risk of famine. In the future, the number of “climate refugees” is expected to rise.

In a series of UN reports, thousands of scientists and government reviewers agreed that limiting global temperature rise to no
more than 1.5°C would help us avoid the worst climate impacts and maintain a livable climate. Yet policies currently in place
point to a 2.8°C temperature rise by the end of the century.

According to the World Economic Forum’s Global Risks Report 2021, the failure to mitigate and adapt to climate change is “the
most impactful” risk facing communities worldwide—ahead of even weapons of mass destruction and water crises. Blame its
cascading effects: As climate change transforms global ecosystems, it affects everything from the places we live to the water we
drink to the air we breathe.

And though climate change affects everyone in some way, it’s indisputable that its most negative impacts are borne
disproportionately by certain groups: women, children, people of color, Indigenous communities, and the economically
marginalized. Climate is a human rights issue.

A. Extreme weather As the earth’s atmosphere heats up, it collects, retains, and drops more water, changing
weather patterns and making wet areas wetter and dry areas drier. Higher temperatures worsen and increase the
frequency of many types of disasters, including storms, floods, heat waves, and droughts. These events can have
devastating and costly consequences, jeopardizing access to clean drinking water, fueling out-of-control wildfires,
damaging property, creating hazardous-material spills, polluting the air, and leading to loss of life.

B. Air pollution and climate change are inextricably linked, with one exacerbating the other. When the earth’s
temperatures rise, not only does our air get dirtier—with smog and soot levels rising accordingly—but it also becomes
filled with more allergenic pollutants, such as circulating mold (thanks to damp conditions from extreme weather and
more floods) and pollen (due to longer, stronger pollen seasons).
respiratory health—particularly for the 300 million people living with asthma worldwide; there’s more airborne pollen and
mold to torment hay fever and allergy sufferers too. Extreme weather events, such as severe storms and flooding, can
lead to injury, drinking water contamination, and storm damage that may compromise basic infrastructure or lead to
community displacement. Indeed, historical models suggest the likelihood of being displaced by a disaster is now 60
percent higher than it was four decades ago—and the largest increases in displacement are being driven by weather-
and climate-related events. (It’s worth noting that displacement comes with its own health threats, such as increases in
urban crowding, trauma, social unrest, lack of clean water, and transmission of infectious diseases.) A warmer, wetter
world is also a boon for insect-borne diseases such as dengue fever, West Nile virus, and Lyme disease.

C. Health risks - According to the World Health Organization, “climate change is expected to cause approximately
250,000 additional deaths per year” between 2030 and 2050. As global temperatures rise, so do the number of fatalities
and illnesses from heat stress, heatstroke, and cardiovascular and kidney disease.

D. Rising seas - The Arctic is heating up twice as fast as any other place on the planet. As its ice sheets melt into the
seas, our oceans are on track to rise by anywhere from 0.95 to 3.61 feet by the end of this century, threatening coastal
ecosystems and low-lying areas. Island nations face particular risk, as do some of the world’s largest cities, including
New York City, Miami, Mumbai in India, and Sydney in Australia. he earth’s oceans absorb between one-quarter and
one-third of our fossil fuel emissions and are now 30 percent more acidic than they were in preindustrial times. This
acidification poses a serious threat to underwater life, particularly creatures with calcified shells or skeletons like oysters,
clams, and coral. It can have a devastating impact on shellfisheries, as well as the fish, birds, and mammals that depend
on shellfish for sustenance. In coastal communities where fishing and seafood production sustain the local economy, this
impact extends to human populations as well, destroying livelihoods and opening the door to economic ruin. Rising
ocean temperatures are also altering the range and population of underwater species and contributing to coral bleaching
events that are capable of killing entire reefs—ecosystems that support more than 25 percent of all marine life.
 Flooding is an increasing issue as our climate is changing. Compared to the beginning of the 20th century, there are
both stronger and more frequent abnormally heavy precipitation events across most of the United States.

Snowpack is an important source of fresh water for many people. As the snow melts, fresh water becomes
available for use, especially in regions like the Western United States where there is not much precipitation in warmer
months. But as temperatures warm, there is less snow overall and snow begins to melt earlier in the year, meaning
snowpack may not be a reliable source of water for the entire warm and dry seasons.

E. Climate change is increasing pressure on wildlife to adapt to changing habitats—

and fast. Many species are seeking out cooler climates and higher altitudes, altering seasonal behaviors, and
adjusting traditional migration patterns. These shifts can fundamentally transform entire ecosystems and the intricate
webs of life that depend on them. As a result, according to a 2020 study, one-third of all animal and plant species could
face extinction by 2070. Another study showed that mammals, fish, birds, reptiles, and other vertebrate species are
disappearing many times faster than they should be, a phenomenon that has been linked to climate change, pollution,
and deforestation—all interconnected threats. In early 2021, climate and biodiversity experts issued a joint report
illustrating these interconnections and urging simultaneous action on both fronts. On the flip side, milder winters and
longer summers have enabled some species to thrive, including tree-killing insects that are endangering entire forests.

NOAA (National Oceanic and Atmospheric Administration) monitors global climate data and here are some of the
changes NOAA has recorded. You can explore more at the Global Climate Dashboard.

A. Global temperatures rose about 1.8°F (1°C) from 1901 to 2020.

B. Sea level rise has accelerated from 1.7 mm/year throughout most of the twentieth century to 3.2 mm/year since 1993.

C. Glaciers are shrinking: average thickness of 30 well-studied glaciers has decreased more than 60 feet since 1980.

D.The area covered by sea ice in the Arctic at the end of summer has shrunk by about 40% since 1979.

E. The amount of carbon dioxide in the atmosphere has risen by 25% since 1958, and by about 40% since the Industrial
Revolution.

F. Snow is melting earlier compared to long-term averages.

January 31, 2022 — The Redlands Mesa area outside Hotchkiss, Colorado, is particularly at risk to wildfires, but with funding
from NOAA’s Environmental Literacy Program, local high school students are taking action to tackle their community’s
vulnerability to this hazard.

In partnership with Michael Muñoz, a geophysical science teacher at the school, the Cooperative Institute for Research in
Environmental Sciences (CIRES) HEART Forceoffsite link project team worked with the local fire department to support
the high school students in their efforts using funding from NOAA’s Environmental Literacy Program. Nineteen freshmen learned
about wildfires, visited the local fire station, and then played a wildfire scenario-based role-play game with local firefighters as
part of their geophysical science course. Through playing the wildfire game, students identified potential strategies to increase
awareness in Redlands Mesa about wildfire risk and to increase the number of residents enrolled in the emergency notification
system.

Solution to climate change

We also have global frameworks and agreements to guide progress, such as the Sustainable Development Goals, the UN
Framework Convention on Climate Change and the Paris Agreement. Three broad categories of action are: cutting emissions,
adapting to climate impacts and financing required adjustments.

Switching energy systems from fossil fuels to renewables like solar or wind will reduce the emissions driving climate change. But
we have to act now. While a growing number of countries is committing to net zero emissions by 2050, emissions must be cut in
half by 2030 to keep warming below 1.5°C. Achieving this means huge declines in the use of coal, oil and gas: over two-thirds of
today’s proven reserves of fossil fuels need to be kept in the ground by 2050 in order to prevent catastrophic levels of climate
change.

A.Paris Agreement
The Biden administration has committed to the principles set forth during the 2015 Paris Climate Change Conference, where
nearly every nation on the earth committed to actions aimed at shifting away from dirty fossil fuels and toward cleaner, smarter
energy options in order to limit global temperature rise this century to 2 degrees Celsius—or 1.5 degrees Celsius, if possible.

On Earth Day in 2021, President Biden committed the United States to cutting its carbon pollution by 50 to 52 percent from 2005
levels—nearly double what President Obama had promised—and to do it by 2030, just five years later than the original deadline
set when the United States first joined the agreement. While bold, the new targets are achievable, but only if Congress, states,
and the business sector join in to help us get there by doing things like setting a national clean energy standard, electrifying our
fleet of cars and trucks, curbing methane emissions, and maximizing building efficiency.

B. Build Back Better agenda by Joe Biden, which ties the post-pandemic economic recovery in the United States to projects
that will curb climate change while putting tens of millions of unemployed or underemployed people to work in good-paying jobs.

C. Herculean task one that depends on international consensus and the efforts of communities, companies, and
individuals alike. To that end, many states, from California to Iowa, are championing clean energy industries, such as
solar and wind; U.S. cities are taking action to mitigate climate change and bolster climate resilience while placing equity
at the forefront; and corporations—including some of the world’s largest multinationals—are pledging to change the way
they do business to achieve net-zero emissions by 2040.

D. You - You can join, amplify, or otherwise support the international youth climate movement that has emerged in the
last few years as a galvanized response to government inaction; in rallies and marches around the world, this movement
is letting leaders know that delay on climate action will no longer be tolerated. You can also pick up the phone to call
Congress about environmental policies that matter, supporting renewable energy projects, and prioritizing fuel and
energy efficiency that will not only curb individual carbon emissions but bolster clean alternatives to dirty fossil fuels.

Intergovernmental Panel on Climate Change (IPCC) — the United Nations body established to assess the science related
to climate change — modern humans have never before seen the observed changes in our global climate, and some of these
changes are irreversible over the next hundreds to thousands of years. The IPCC’s Sixth Assessment report, published in 2021,
found that human emissions of heat-trapping gases have already warmed the climate by nearly 2 degrees Fahrenheit (1.1
degrees Celsius) since 1850-1900.1 The global average temperature is expected to reach or exceed 1.5 degrees C (about 3
degrees F) within the next few decades. These changes will affect all regions of Earth.

The scientific evidence is unequivocal: climate change is a threat to human wellbeing and the health of the planet. Any further
delay in concerted global action will miss the brief, rapidly closing window to secure a liveable future."