Introduction to Climate Change
What is climate change?
Climate Change is defined by the IPCC as: A change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.
These variations of Earth's climate are due to natural causes and human actions and have an impact on all climatic parameters. There is currently a strong scientific consensus that the Earth is warming faster than at any other time in recent history and that this warming is mainly caused by greenhouse gas emissions produced from human activities.
Global Land and Ocean Temperature from 1990 to 2019
What are the greenhouse gases?
On Earth, human activities are increasing the natural background concentration of greenhouse gases. Greenhouse gases are gases in Earth’s atmosphere that trap heat. They let sunlight pass through the atmosphere (i.e. ‘shortwave solar radiation), but they prevent the heat that the Earth emits (i.e. ‘outgoing longwave radiation’) from leaving the atmosphere, instead reradiating it back to Earth’s surface.
Over the last century the burning of fossil fuels, such as coal and oil has increased the concentration of atmospheric carbon dioxide (CO2) in earth’s atmosphere.
Since 1750 when the Industrial Revolution began, CO2 levels have risen more than 45%. The concentration of CO2 in the atmosphere is now higher than at any time in at least 800,000 years.
Aside from CO2, the other main greenhouse gases are:
Water vapor: The most abundant and potent greenhouse gas in Earth’s atmosphere. Its behavior is fundamentally different from the other greenhouse gases since it acts as a feedback to the climate. As warm air can hold more water vapor, the current warming results in an increased concentration of water vapor in the lower atmosphere, capable of absorbing longwave radiation and emitting it downward. As the Earth's atmosphere warms, its water vapor concentration increases, making water vapor one of the most important positive feedback mechanisms enhancing the greenhouse effect.
Source: Figure 1, FAQ 1.3, IPCC Fourth Assessment Report (2007), Chapter 1
Methane:A hydrocarbon gas produced both through natural sources and human activities, including the decomposition of waste in landfills, agriculture and from ruminant livestock.
Nitrous oxide: Produced by soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.
Fluorinated gases: Chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs) and Perfluorocarbons (PFCs), as well as sulfur hexafluoride (SF6) are powerful greenhouse gases that are emitted from a variety of industrial processes.
Evidence and consequences
Global Temperature Rise
The temperature of the Earth's surface, oceans and atmosphere, has risen about 2 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century. This heating is caused by human activities, primarily the burning of fossil fuels that pump carbon dioxide (CO2), methane and other greenhouse gases into the atmosphere.
At the 2015 United Nation Climate Change Conference in Paris, 195 nations signed a universal agreement known as the Paris Agreement. Its main goal is to keep the increase in global average temperature to well below 2 °C above pre-industrial levels; and to pursue efforts to limit the increase to 1.5 °C, recognizing that this would substantially reduce the risks and impacts of climate change.
Melting ice and rising seas
The world's ice sheets are melting fast. Average temperatures in the Arctic are rising twice as fast as they are elsewhere on Earth. Global sea level rose about 8 inches (~20 cm) in the last century. The rate in the last two decades, however, is nearly double that of the last century and is accelerating slightly every year. By 2100, it's estimated that our oceans will be one to four feet (~30 to 120 cm) higher. Coastal cities around the world will have to adapt to rising sea levels. According to the World Economic Forum's Global Risk Report 2019, around 90% of all coastal areas will be affected to varying degrees.
Extreme weather events
As the temperature is increasing, extreme weather events such as droughts, floods and heat waves are becoming more frequent, while others such as hurricanes may become more severe. As the weather patterns are changing, the water quality and water supply will affect ecosystems and livelihoods in some regions worldwide.
Ocean Acidification
Ocean acidification is the ongoing decrease in the pH of the Earth's ocean caused by the uptake of carbon dioxide (CO2) from the atmosphere that humans produce by burning fossil fuels. Since the beginning of the Industrial Revolution, the acidity of the surface ocean has already increased by about 30 percent according to NOAA's Pacific Marine Environmental Laboratory.
Our oceans absorb about a quarter of the CO2 emitted by human activities each year. This ocean acidification is expected to have dramatic and mostly negative impacts on ocean ecosystems causing death and disease among organisms that require carbonate ions to build their calcite shells or skeletons, such as coral and other organisms in the sea.
Also, food security around the world might be compromised since billions of people rely on fishing as their primary source of food. Aside from the negative ecological consequences of acidification, the ocean may be arriving at a saturation point regarding the amount of CO2 it can absorb and thus its role as a carbon sink may become compromised in the future.
Change in ecosystems and extinction of species
Ecosystems are also affected by climate change. Habitats are being modified and some species might become extinct if they are not able to adapt or displace fast enough.
Species that are unable to do this are likely to perish, and in some cases may become globally extinct. According to the Intergovernmental Panel on Climate Change's 2014 assessment, many land, freshwater, and ocean species are already changing seasonal behaviors and traditional migration patterns, looking for cooler climates or higher altitudes, in an attempt to escape warming.
Resources:
IPCC, 2012: Glossary of terms. In: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C.B., V. Barros, T.F. Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.)]. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change (IPCC). Cambridge University Press, Cambridge, UK, and New York, NY, USA, pp. 555-564.
Learn more with the Gossary of terms created by the IPPC.
FULL MOVIE: CHASING TRACES FROM THE PAST:
In this documentary movie , Ernesto Tejedor, researcher from the PIRE CREATE Project and researchers from the University of Zaragoza will make a journey through isolated lakes, ancient forests, remote glaciers, deep caves and rare historical manuscripts, chasing those evidences that allow us to infer past climate conditions beyond the instrumental period. Besides, some of the most important scientists in their fields, will accompany us in this adventure to discover the climate secrets stored in those evidences. Understanding the climate of the past will help contextualizing the current warming and that would mean better adaptation in the future.