A changing climate impacts crop growth and human health, while many people may need to leave their homes. It places certain species at an increased risk of extinction. The effects of climate change are real, and they are already happening.
Climate change can affect our planet in lots of different ways:
Warming oceans and changes in ocean currents
As Earth’s climate warms, the water also warms melting sea ice. This warming could make the water less cold and less dense and thus less likely to sink. Without sinking cold water, the ocean currents could slow down or stop in some places.
Changes in the hydrological cycle
Climate change is likely causing parts of the water cycle to speed up as warming global temperatures increase the rate of evaporation worldwide. More evaporation is causing more precipitation, on average.
Rising sea levels
Oceans absorb 90% of the extra heat generated by human influence. However, when water heats up, it expands to take up more volume. So, when oceans heat up, they expand too, causing the sea level to rise.
We also have extra water flowing into the ocean from melting ice sheets and glaciers. Between 1901 and 2018, the global average sea level has risen by around 20 centimetres.
Melting sea ice and glaciers
Some parts of the planet, such as the north and south pole, warm more quickly than other places. At the poles, glaciers and ice sheets reflect energy from the sun into space. So, when there is less ice, less energy from the sun is reflected away. The area then heats even more quickly, causing even more ice to melt.
The ice in the Arctic is melting fast. It is already 65% thinner than it was in 1975. Late summer Arctic sea ice area is currently the smallest in at least 1,000 years.
If we do not reduce emissions soon, we could see ice-free summers in the Arctic by the middle of this century.
Reduction in salinity of sea and oceans
When ice sheets and glaciers melt, freshwater flows into the sea. As well as making the sea level rise, freshwater also reduces the salinity (saltiness) of the water, which can slow or change ocean currents.
Ocean acidification
Oceans also absorb around 25% of the carbon dioxide that humans release into the air. The oceans then become less alkaline, a process called ‘ocean acidification’. Ocean acidification is bad because it can have negative effects on marine organisms, like coral and plankton, which are an important part of the food chain.
Erratic rainfall
Warmer air can hold more water, so rainfall is increasing on average across the world. In some places, rainfall is becoming more intense as well. However, some areas receive less rain because of changes in wind patterns.
Forest mortality and increased risk of fires
Heat and dry soil make conditions conducive for the spread of forest fires.
Climate change and land-use change are projected to make wildfires more frequent and intense, with a global increase of extreme fires of up to 14 per cent by 2030, 30 per cent by the end of 2050 and 50 per cent by the end of the century, according to a new report by the UN Environment Programme (UNEP) and GRID-Arendal.
Change in seasonality
Although the timing, duration, and intensity of the seasons vary naturally from year to year, climate
change is driving longer-term changes in seasonality and fundamentally altering the ways in which
humans and natural systems experience and interact with seasonal events.
At the core of these changes are increases in temperature. These changes in physical climate lead to wide-ranging impacts such as warmer winters; precipitation patterns shifting from snow to rain; species shifting the timing or location of their seasonal activities, such as migration and reproduction; geographic
expansion and outbreaks of pests; and increases in the likelihood or duration of extreme events
such as heat waves, hurricanes, and wildfires.
More extreme weather
The number of heat waves, heavy downpours, and major cyclones has increased and the strength of these events has increased too.
Loss of biodiversity
Over half of global GDP is dependent on nature. More than 1 billion people rely on forests for their livelihoods. And land and the ocean absorb more than half of all carbon emissions.
Up to one million species are threatened with extinction, many within decades. Irreplaceable ecosystems like parts of the Amazon rainforest are turning from carbon sinks into carbon sources due to deforestation. And 85 per cent of wetlands, such as salt marshes and mangrove swamps which absorb large amounts of carbon, have disappeared.
On land, higher temperatures have forced animals and plants to move to higher elevations or higher latitudes, many moving towards the Earth’s poles, with far-reaching consequences for ecosystems. The risk of species extinction increases with every degree of warming.
In the ocean, rising temperatures increase the risk of irreversible loss of marine and coastal ecosystems. Live coral reefs, for instance, have nearly halved in the past 150 years, and further warming threatens to destroy almost all remaining reefs.
Damage to marine ecosystems
Rising water temperatures, acidification, and low oxygen levels can combine with natural ocean cycles to create extreme marine events. Marine heat waves, dead zones, and coral bleaching are just a few examples of these events, which are projected to become more common and severe.
Localised flooding and flooding of coastal regions
Rising sea level inundates low-lying wetlands and dry land, erodes shorelines, contributes to coastal flooding, and increases the flow of salt water into estuaries and nearby groundwater aquifers.
Global greening
From a quarter to half of Earth’s vegetated lands has shown significant greening over the last 35 years largely due to rising levels of atmospheric carbon dioxide.
