Global climate, vulnerability and responses Flashcards
Meaning of climate change
Climate change refers to long-term shifts in global or regional climate patterns, characterized by changes in average weather conditions such as temperature, precipitation, and wind patterns12. It is primarily caused by human activities, especially the burning of fossil fuels, which release greenhouse gases into the atmosphere3. These gases trap heat, leading to a gradual increase in the Earth’s average surface temperature, a phenomenon known as global warming. The consequences of climate change are far-reaching and affect various aspects of our planet’s systems.
Meaning of hydrosphere
The hydrosphere is the total water on Earth, encompassing all oceans, rivers, lakes, glaciers, groundwater, and water vapor in the atmosphere. This definition is brief and captures the essential elements of the hydrosphere.
Meaning of atmosphere
The atmosphere is the layer of gases surrounding Earth, composed mainly of nitrogen (78%) and oxygen (21%), that protects life by filtering harmful solar radiation and regulating temperature. This definition is succinct and captures the essential aspects of the atmosphere.
Meaning of biosphere
The biosphere is the global sum of all ecosystems, encompassing all living organisms (plants, animals, and microorganisms) and their interactions with the environment, including land, water, and the atmosphere. This definition captures the essence of the biosphere in a clear and succinct manner.
Water stored in ice, oceans and changing sea levels
Ice:
- Ice is melting at accelerated rates due to global warming.
-Rising global temperatures cause ice to melt faster than it can be replenished by snowfall.
- As ice melts, darker surfaces are exposed, absorbing more heat and leading to further melting.
- Warmer ocean waters contribute to melting ice shelves and glaciers from below.
- Between 2000 and 2019, glaciers lost about 267 billion tonnes of ice annually.
- Ice sheets in Greenland and the Antarctic are shrinking and snow cover is decreasing
Oceans:
- As temperature rises in oceans, the absorption of carbon dioxide decreases, and results in carbon being released leading to global warming.
- Oceans have absorbed about 25% of the carbon dioxide emissions produced by human activities. This absorption has slowed the progress of climate change
- As oceans warm, their capacity to absorb CO2 decreases.
Changing sea levels:
- Greenland and Antarctic ice sheets lost 6.4 trillion tonnes of ice (1992-2017). This ice loss raised global sea levels by 17.8mm.
- Glaciers contributed 27mm to sea level rise (1961-2016).
- As oceans warm, water expands, increasing volume contributing to sea levels rising.
- Glaciers account for 25-30% of observed sea level rise.
- Fastest sea level rise expected in southern US East Coast and Gulf Coast.
Carbon stored in ice, oceans and the biosphere
Ice:
- Ice plays a crucial role in carbon storage, primarily through Permafrost as well as glaciers and ice sheets.
- Permafrost is frozen soil in Arctic regions that contains about 1400 petagrams of carbon. At low temperatures it prevents organic matter from decomposing, pausing the fast carbon cycle. Thawing permafrost could release significant amount of carbon into the atmosphere.
- Glaciers worldwide store approximately 6 petagrams of carbon, with most in the Antarctic Ice Sheet.
- Ice traps organic matter slowing its decomposition.
Oceans:
- Oceans are the largest carbon reservoirs.
- Oceans contain about 38,000 petagrams of carbon, 60 times more than the atmosphere.
- Warming oceans may reduce CO2 absorption.
- Ocean circulation moves carbon-rich water to deep sea.
- Phytoplankton absorb CO2 during photosynthesis.
Biosphere:
- The biosphere, particularly terrestrial ecosystems, is a significant carbon store.
- Forests and other plant life store carbon through photosynthesis.
- Approximately 560 petagrams of carbon are stored in trees and organic material.
- Soil contains up 1500 petagrams of carbon and is formed in organic matter and microorganisms.
Who is most at risk for increased sea levels?
People who live close to the coastline. Over 40% of the world’s population lives within 100 km of a coastline, so there is an increased risk of flooding. This risk is particularly high in low-lying coastal areas such as the Netherlands, Bangladesh and the Maldives.
What are the consequences of coastal flooding?
- Damage to infrastructure, homes and industry, leading to loss of livelihood
- Risk to human life, such as death from drowning
salinisation of agricultural land, reducing its capacity to grow many types of crops - Contamination of freshwater resources by salt water, including saline intrusion of groundwater resources: this would render fresh water too salty for domestic, agricultural and industrial uses
- Degradation of coastal ecosystems such as wetlands, estuaries, mangroves and beaches
- Damage to inland ecosystems, threatening wildlife.
What are the two outcomes that the IPCC (Intergovernmental Panel on Climate Change) suggested that will occur by 2100`
- If greenhouse gas emissions are reduced and there is an increase in carbon dioxide absorption through forestation schemes the mean global temperature will only increase by 0.3 to 1.7°C.
- If high greenhouse gas emissions continue, temperatures could rise by 2.6 to 4.8°C.
What will happen with a rise in temperature?
With a rise in temperature, more water will evaporate, resulting in some regions experiencing greater rainfall. However, this rainfall will not be distributed equally and some areas that are already water-stressed are likely to receive even less rainfall.
What will increase in probability with increased temperatures?
- The annual amount of precipitation will increase in high altitudes, the equatorial Pacific and other already wet regions of the subtropics (wet subtropical regions typically have between 80 and 165 cm of rainfall per year compared to dry subtropical regions, which have between 30 and 90 cm of rainfall per year)
- The annual amount of precipitation will decrease in the mid-latitudes and dry regions of the subtropics
- Extreme weather events will be more frequent, longer in duration and more intense (e.g. heatwaves and rainstorms); this will result in more drought and floods.
What is the general pattern with increased global temperatures?
- Thermal expansion of the oceans: water absorbs heat and expands
- Melting of snow and ice:
- The glaciers of Mount Kilimanjaro in East Africa
and the Andes in South America are retreating - Ice sheets in Greenland and the Antarctic are
shrinking and snow cover is decreasing - Shipping routes are opening up, thus improving
global communications.
- The glaciers of Mount Kilimanjaro in East Africa
What does rising global temperatures affect besides raising sea levels?
Rising global temperatures not only raise sea levels but also change precipitation patterns. This is likely to affect (reduce) the quantity and quality of fresh water available. The availability of water could be influenced by the following factors:
- A reduction in precipitation in semi-arid and arid regions will reduce available water resources. This could be further exacerbated by higher temperatures, which increase evaporation rates. The frequency and intensity of drought conditions is expected to increase.
- A reduction in glacier or snow water storage will lead to reduced water resources downstream during spring and summer. Loss of glacial melt in the Andes Mountains is expected to have devastating effects in Peru, a country already considered to be the most water-stressed in South America. The reduction in river flow will affect both water resources and production of hydroelectric power.
How else is the balance on Earth possible?
In addition to the four major spheres there are a number of global cycles that maintain balance and make life on Earth possible. For example, the hydrological cycle moves water through the hydrosphere. In the context of global climate change the carbon cycle is very important, especially when considering the changes in carbon storage (carbon sinks) in the hydrosphere, biosphere and geosphere.
A major change in carbon sinks is happening in the geosphere. The geosphere stores the majority of the Earth’s carbon: some 80% is in limestone and other calcium carbonate-based rocks. The rest is in fossil fuels. Carbon stays locked up in rocks for millions of years under natural conditions. However, humans extract fossil fuels to support our lifestyles and its combustion releases vast amounts of carbon. This has long been seen as the main cause of global climate change.
What sources do oceans gain the carbon dioxide from?
- The oceans absorb 93% of the atmospheric carbon and are the second largest sink in the carbon cycle.
- Carbon dioxide is gained from the atmosphere as it dissolves at the air–water interface and is converted into carbonates.
- Other parts of the hydrosphere contribute carbon dioxide as rivers flow into the ocean laden with dissolved organic carbon.
- The biosphere also contributes carbon dioxide: plants convert carbon dioxide into organic carbon through photosynthesis, which then moves through food chains or into deep ocean sediments as organisms die and sink to the bottom. The biosphere also converts dissolved carbon into calcium carbonate for shells and other hard bony structures in sea creatures.
