Global Warming

This section looks at a global warming definition, causes of global warming, effects of global warmingsolutions to global warming and global warming facts. The latest global warming news is included at the foot of the page.

Global warming definition: describes the average global surface temperature increase from human emissions of greenhouse gases. Note the association with the term 'climate change'. Climate change refers to wider issues, including global warming, created by rising greenhouse gas emissions. 

NASA graph of average global temperatures: the raw facts

Over the past 50 years, the average global temperature has increased at the fastest rate in recorded history. And experts see the trend is accelerating: All but one of the 17 hottest years in NASA’s 135-year record have occurred since 2000. This graph illustrates the change in global surface temperature relative to 1951-1980 average temperatures. The year 2016 ranks as the warmest on record.


Causes of global warming

The planet's average surface temperature has risen about 2.0 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere. Most of the warming occurred in the past 35 years, with 16 of the 17 warmest years on record occurring since 2000.

Global warming history

Credit: NASA.

The Earth's climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 11,000 years ago marking the beginning of the modern climate era — and of human civilisation.


Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.


The current warming trend is of particular significance because most of it is extremely likely (currently around 97 percent probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades to millennia.


Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale.


This body of data, collected over many years, reveals the signals of a changing climate.


The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century.


Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many instruments flown by NASA.


There is no question that increased levels of greenhouse gases must cause the Earth to warm in response.


Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels.


Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks.


This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming.

The causes of global warming

Credit: NASA.

Most climate scientists agree the main cause of the current global warming trend is human expansion of the "greenhouse effect" — 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."


Gases that contribute to the greenhouse effect include:


Carbon dioxode (CO2)

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 CO2 concentration by more than a third since the Industrial Revolution began. This is the most important long-lived "forcing" of climate change.


Methane (CH4)

A hydrocarbon gas produced both through natural sources and human activities, including the decomposition of wastes in landfills, agriculture, and especially rice cultivation, as well as ruminant digestion and manure management associated with domestic livestock. On a molecule-for-molecule basis, methane is a far more active greenhouse gas than carbon dioxide, but also one which is much less abundant in the atmosphere.


Water vapour (H20)

The most abundant greenhouse gas, but importantly, it acts as a feedback to the climate. Water vapour increases as the Earth's atmosphere warms, but so does the possibility of clouds and precipitation, making these some of the most important feedback mechanisms to the greenhouse effect.


Nitrous oxide (N20)

A powerful greenhouse gas produced by soil cultivation practices, especially the use of commercial and organic fertilisers, fossil fuel combustion, nitric acid production, and biomass burning.


Chlorofluorocarbons (CFC's)

Synthetic compounds entirely of industrial origin used in a number of applications, but now largely regulated in production and release to the atmosphere by international agreement for their ability to contribute to destruction of the ozone layer. They are also greenhouse gases.

National Geographic: climate change 101 video

Effects of global warming

Global warming will undoubtably shake the delicate web of life with unknown impact on biodiversity. Applying new pressures at the level of ecosystems, populations and species. Depending on adaptation responses, there will be winners and losers. Some crops and other plants may respond favorably to increased atmospheric CO2, growing more vigorously and using water more efficiently. At the same time, higher temperatures and shifting climate patterns may change the areas where crops grow best and affect the makeup of natural plant communities.

Global warming - to state the blindingly obvious - effects temperature rises

Some regions may welcome warmer temperatures, but others may not. Warmer conditions will probably lead to more evaporation and precipitation overall, but individual regions will vary, some becoming wetter and others dryer.


The planet's average surface temperature has risen about 2.0 degrees Fahrenheit,1.1 degrees Celsius since the late 19th century, a change driven largely by increased carbon dioxide emissions into the atmosphere.


Most of the warming occurred in the past 35 years, with 16 of the 17 warmest years on record occurring since 2000. 

Global warming effects rising sea temperatures

The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969.


Global warming effects rising sea levels


A stronger greenhouse effect will warm the oceans and partially melt glaciers and other ice, increasing sea level. 


Ocean water also will expand if it warms, contributing further to sea level rise.


Global sea level rose about 8 inches in the last century. The rate in the last two decades, however, is nearly double that of the last century.

Global warming effects reduced ice sheet coverage 

The Greenland and Antarctic ice sheets have decreased in mass.


Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006.


Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005.


Global warming effects Arctic sea ice


Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades.




Global warming effects decreased snow cover

Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier.


Global warming effects reduced glacial coverage 


Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa.


Global warming effects ocean acidification

Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent.


This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans.


The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.

Global warming effects extreme weather events

The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950.


The U.S. has also witnessed increasing numbers of intense rainfall events.

Future global warming effects: into the 21st century

Global warming - what's around the corner? Case study: Unites States

Change will continue through this century and beyond

Global climate is projected to continue to change over this century and beyond. The magnitude of climate change beyond the next few decades depends primarily on the amount of heat-trapping gases emitted globally, and how sensitive the Earth’s climate is to those emissions.



Frost-free season (and growing season) will lengthen


Based on U.S. studies, the length of the frost-free season (and the corresponding growing season) has been increasing nationally since the 1980s, with the largest increases occurring in the western United States, affecting ecosystems and agriculture. Across the United States, the growing season is projected to continue to lengthen.


In a future in which heat-trapping gas emissions continue to grow, increases of a month or more in the lengths of the frost-free and growing seasons are projected across most of the U.S. by the end of the century, with slightly smaller increases in the northern Great Plains. The largest increases in the frost-free season (more than eight weeks) are projected for the western U.S., particularly in high elevation and coastal areas. The increases will be considerably smaller if heat-trapping gas emissions are reduced.  


Changes in precipitation patterns


Average U.S. precipitation has increased since 1900, but some areas have had increases greater than the national average, and some areas have had decreases. More winter and spring precipitation is projected for the northern United States, and less for the Southwest, over this century.

Projections of future climate over the U.S. suggest that the recent trend towards increased heavy precipitation events will continue. This trend is projected to occur even in regions where total precipitation is expected to decrease, such as the Southwest.


More droughts and heat waves


Droughts in the Southwest and heat waves (periods of abnormally hot weather lasting days to weeks) everywhere are projected to become more intense, and cold waves less intense everywhere. Summer temperatures are projected to continue rising, and a reduction of soil moisture, which exacerbates heat waves, is projected for much of the western and central U.S. in summer. By the end of this century, what have been once-in-20-year extreme heat days (one-day events) are projected to occur every two or three years over most of the nation.  


Hurricanes will become stronger and more intense


The intensity, frequency and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. The relative contributions of human and natural causes to these increases are still uncertain. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate continues to warm.


Sea level will rise 1-4 feet by 2100


Global sea level has risen by about 8 inches since reliable record keeping began in 1880. It is projected to rise another 1 to 4 feet by 2100. This is the result of added water from melting land ice and the expansion of seawater as it warms.

In the next several decades, storm surges and high tides could combine with sea level rise and land subsidence to further increase flooding in many of these regions. Sea level rise will not stop in 2100 because the oceans take a very long time to respond to warmer conditions at the Earth’s surface. Ocean waters will therefore continue to warm and sea level will continue to rise for many centuries at rates equal to or higher than that of the current century.  


Arctic likely to become ice-free


The Arctic Ocean is expected to become essentially ice free in summer before mid-century. 

Solutions to global warming

Government actions to reduce global warming

United Nations (UN) Framework Convention on Climate Change: a brief history

Source: UN website.


In 1992, countries joined an international treaty, the United Nations Framework Convention on Climate Change (UNFCCC), to consider what they could do to limit global temperature increases and the resulting climate change, and to cope with its impacts.


By 1995, countries realised that emission reductions provisions in the Convention were inadequate. As a result, they launched negotiations to strengthen the global response to climate change, and, in 1997, adopted the Kyoto Protocol.


The Kyoto Protocol legally binds developed countries to emission reduction targets. The Protocol’s first commitment period started in 2008 and ended in 2012. The second commitment period began on 1 January 2013 and will end in 2020.


There are now 195 Parties to the Convention and 192 Parties to the Kyoto Protocol. The Protocol entered into force on 16 February 2005. Since then, the Protocol  the Parties to the Protocol  have continued the negotiations and have amended the Protocol to achieve more ambitious results by 2030.

The following timeline provides a brief summary of negotiations towards a climate agreement.


Negotiations timeline

1979 — The first World Climate Conference takes place.

1988 — The Intergovernmental Panel on Climate Change (IPCC) is set up. Learn more about the science of climate change.

1990 — The IPCC and the second World Climate Conference call for a global treaty on climate change. The United Nations General Assembly negotiations on a framework convention begin.

1991 — First meeting of the Intergovernmental Negotiating Committee takes place.

1992 —At the Earth Summit in Rio, the UNFCCC is opened for signature along with its sister Rio Conventions, the UN Convention on Biological Diversity and the UN Convention to Combat Desertification.

1994 — The UNFCCC enters into force.

1995 — The first Conference of the Parties (COP 1) takes place in Berlin.

1996 — The UNFCCC Secretariat is set up to support action under the Convention.

1997 — The Kyoto Protocol is formally adopted in December at COP3.

2001 — The Marrakesh Accords are adopted at COP7, detailing the rules for implementation of the Kyoto Protocol, setting up new funding and planning instruments for adaptation, and establishing a technology transfer framework.

2005 — Entry into force of the Kyoto Protocol. The first Meeting of the Parties to the Kyoto Protocol (MOP 1) takes place in Montreal. In accordance with Kyoto Protocol requirements, Parties launched negotiations on the next phase of the KP under the Ad Hoc Working Group on Further Commitments for Annex I Parties under the Kyoto Protocol (AWG-KP). What was to become the Nairobi Work Programme on Adaptation (it would receive its name in 2006, one year later) is accepted and agreed on.

2007 — The IPCC’s Fourth Assessment Report is released. Climate science entered into popular consciousness. At COP13, Parties agreed on the Bali Road Map, which charted the way towards a post-2012 outcome in two work streams: the AWG-KP, and another under the Convention, known as the Ad-Hoc Working Group on Long-Term Cooperative Action Under the Convention. 

2009 — Copenhagen Accord drafted at COP15 in Copenhagen. Countries later submitted emissions reductions pledges or mitigation action pledges, all non-binding.

2010 — Cancun Agreements drafted and largely accepted by the COP, at COP16. Through the Agreements, countries made their emission reduction pledges official, in what was the largest collective effort the world has ever seen to reduce emissions in a mutually accountable way.

2011 — The Durban Platform for Enhanced Action drafted and accepted by the COP, at COP17. In Durban, governments clearly recognized the need to draw up the blueprint for a fresh universal, legal agreement to deal with climate change beyond 2020, where all will play their part to the best of their ability and all will be able to reap the benefits of success together.

2012 – The Doha Amendment to the Kyoto Protocol is adopted by the CMP at CMP8. The amendment includes: new commitments for Annex I Parties to the Kyoto Protocol who agreed to take on commitments in a second commitment period from 1 January 2013 to 31 December 2020; a revised list of greenhouse gases to be reported on by Parties in the second commitment period; and amendments to several articles of the Kyoto Protocol pertaining to the first commitment period and which needed to be updated for the second commitment period.

2013 – Key decisions adopted at COP19/CMP9 include decisions on further advancing the Durban Platform, the Green Climate Fund and Long-Term Finance, the Warsaw Framework for REDD Plus and the Warsaw International Mechanism for Loss and Damage. More on the Warsaw Outcomes.

2014 – COP20 held in December in Lima, Peru

2015 – COP21 or CMP11 held in Paris, France in November/December. 


The conference negotiated the Paris Agreement, a global agreement on the reduction of climate change.The key result was an agreement to set a goal of limiting global warming to less than 2 degrees Celsius (°C) compared to pre-industrial levels. The agreement calls for zero net anthropogenic greenhouse gas emissions to be reached during the second half of the 21st century.


In the adopted version of the Paris Agreement, the parties will also "pursue efforts to" limit the temperature increase to 1.5 °C.[2] The 1.5 °C goal will require zero emissions sometime between 2030 and 2050, according to some scientists.

Personal actions to reduce global warming

Top 10 tips

01 Reduce, Reuse, Recycle

Do your part to reduce waste by choosing reusable products instead of disposables - get a reusable water bottle, for example. Buying products with minimal packaging (including the economy size when that makes sense for you) will help to reduce waste. And whenever you can, recycle paper, plastic, newspaper, glass and aluminum cans. If there isn't a recycling program at your workplace, school, or in your community, ask about starting one. By recycling half of your household waste, you can save 2,400 pounds of carbon dioxide annually.


02 Use Less Heat and Air Conditioning

Adding insulation to your walls and attic, and installing weather stripping or caulking around doors and windows can lower your heating costs more than 25 percent, by reducing the amount of energy you need to heat and cool your home.

Turn down the heat while you're sleeping at night or away during the day, and keep temperatures moderate at all times. Setting your thermostat just 2 degrees lower in winter and higher in summer could save about 2,000 pounds of carbon dioxide each year.


03 Change a Light Bulb

Wherever practical, replace regular light bulbs with LED bulbs; they are even better than compact fluorescent light (CFL). Replacing just one 60-watt incandescent light bulb with a LED used 4 hrs a day can yield decent savings annually. LEDs will also last many times longer than incandescent bulbs. 


04 Drive Less and Drive Smart

Less driving means fewer emissions. Besides saving gasoline, walking and biking are great forms of exercise. Explore your community mass transit system, and check out options for carpooling to work or school. Even vacations can provide opportunities to reduce your carbon footprint.

When you do drive, make sure your car is running efficiently. For example, keeping your tyres properly inflated can improve your gas mileage by more than 3 percent. Every gallon of gas you save not only helps your budget, it also keeps 20 pounds of carbon dioxide out of the atmosphere.


05 Buy Energy-Efficient Products

When it's time to buy a new car, choose one that offers good gas mileage. Home appliances now come in a range of energy-efficient models, and LED bulbs are designed to provide more natural-looking light while using far less energy than standard light bulbs.Look into your state's energy efficiency programs, you might find some help.

Avoid products that come with excess packaging, especially molded plastic and packaging that can't be recycled. If you reduce your household garbage by 10 percent, you can save 1,200 pounds of carbon dioxide annually.


06 Use Less Hot Water

Set your water heater at 20 degrees to save energy, and wrap it in an insulating blanket if it is more than 5 years old. Buy low-flow showerheads to save hot water and about 350 pounds of carbon dioxide yearly. Wash your clothes in warm or cold water to reduce your use of hot water and the energy required to produce it. That change alone can save at least 500 pounds of carbon dioxide annually in most households. Use the energy-saving settings on your dishwasher and let the dishes air-dry.


07 Use the "Off" Switch

Save electricity and reduce global warming by turning off lights when you leave a room, and using only as much light as you need. And remember to turn off your television, video player, stereo, and computer when you're not using them.

It's also a good idea to turn off the water when you're not using it. While brushing your teeth, shampooing the dog or washing your car, turn off the water until you actually need it for rinsing. You'll reduce your water bill and help to conserve a vital resource.


08 Plant a Tree

If you have the means to plant a tree, start digging. During photosynthesis, trees and other plants absorb carbon dioxide and give off oxygen. They are an integral part of the natural atmospheric exchange cycle here on Earth, but there are too few of them to fully counter the increases in carbon dioxide caused by automobile traffic, manufacturing, and other human activities. Help mitigate climate change: a single tree will absorb approximately one ton of carbon dioxide during its lifetime. 


09 Get a Smartmeter or Energy Audit from Your Utility Company

Many utility companies will provide free smartmeters and free home energy audits to help consumers identify areas in their homes that may not be energy efficient. In addition, many utility companies offer rebate programs to help pay for the cost of energy-efficient upgrades. 


10 Encourage Others to Conserve

Share information about recycling and energy conservation with your friends, neighbors, and co-workers, and take opportunities to encourage public officials to establish programs and policies that are good for the environment.

These 10 steps will take you a long way toward reducing your energy use and your monthly budget. And less energy use means less dependence on the fossil fuels that create greenhouse gasses and contribute to global warming.

Global warming facts

Taken as a whole, the range of published evidence indicates that the net damage costs of climate change are likely to be significant and to increase over time.
- Intergovernmental Panel on Climate Change (IPCC)

16 of the hottest 17 years on NASA's 135-year record history have happened since 2000 

2016 was the warmest year on record, but notably, eight of the 12 months that make up the year — from January through September, with the exception of June — were the warmest on record for those respective months.

Average global temperatures have risen by 1.1 degrees Celcius since 1900

A change driven largely by increased carbon dioxide emissions into the atmosphere through man-made burning of fossil fuels.

The latest scientific concensus from the IPCC suggests temperatures will rise between 0.3 and 4.8 degrees Celcius by 2100

The Intergovernmental Panel on Climate Change (IPCC) includes more than 1,300 scientists from around the world. In 2013, the panel concluded that "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century."  Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to 1.7 °C (0.5 to 3.1 °F) for their lowest emissions scenario and 2.6 to 4.8 °C (4.7 to 8.6 °F) for the highest emissions scenario.

Global sea levels expected to rise between 1 and 4 feet by 2100

Global sea level has risen by about 8 inches since reliable record keeping began in 1880.


It is projected to rise another 1 to 4 feet by 2100. This is the result of added water from melting land ice and the expansion of seawater as it warms.

Global Warming News -- ScienceDaily

2020 Arctic sea ice minimum at second lowest on record (Mon, 21 Sep 2020)
The 2020 minimum extent, which was likely reached on Sept. 15, 2020 measured 1.44 million square miles (3.74 million square kilometers).
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Climate: Support for simple funding plans -- even if costs are high (Mon, 21 Sep 2020)
There is growing demand for countries to take aggressive action to combat climate change, but less consensus on how to fund it. In a new study, researchers asked more than 10,000 people from the US, UK, Germany and France to weigh in. The majority preferred a constant-cost plan - even if costs are high. The finding surprised researchers, but provides valuable insight for policymakers.
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How to get a handle on carbon dioxide uptake by plants (Mon, 21 Sep 2020)
How much carbon dioxide, a pivotal greenhouse gas behind global warming, is absorbed by plants on land? It's a deceptively complicated question, so a group of scientists recommends combining two cutting-edge tools to help answer the crucial climate change-related question.
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Studies investigate marine heatwaves, shifting ocean currents (Mon, 21 Sep 2020)
Two new studies investigate marine heatwaves and currents at the edge of the continental shelf, which impact regional ocean circulation and marine life.
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Undersea earthquakes shake up climate science (Fri, 18 Sep 2020)
Sound generated by seismic events on the seabed can be used to determine the temperature of Earth's warming oceans.
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Curbing land clearing for food production is vital to reverse biodiversity declines (Thu, 17 Sep 2020)
Preserving terrestrial biodiversity requires more ambitious land-conservation targets to be established and met. At the same time, 'bending the curve' on biodiversity loss needs more efficient food production, and healthier and less wasteful consumption and trade. If undertaken with 'unprecedented ambition and coordination,' these efforts provide an opportunity to reverse terrestrial biodiversity loss by 2050.
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Emissions could add 15 inches to 2100 sea level rise (Thu, 17 Sep 2020)
An international effort that brought together more than 60 ice, ocean and atmosphere scientists from three dozen international institutions has generated new estimates of how much of an impact Earth's melting ice sheets.
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How much will polar ice sheets add to sea level rise? (Thu, 17 Sep 2020)
Over 99% of terrestrial ice is bound up in the ice sheets covering Antarctic and Greenland. Even partial melting of this ice due to climate change will significantly contribute to sea level rise. But how much exactly? For the first time ever, glaciologists, oceanographers, and climatologists from 13 countries have teamed up to make new projections.
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