Climate

Weather & Climate

What is weather and climate?

Weather refers to the state of atmospheric conditions at a specific location and time, encompassing factors such as air temperature, cloud cover, precipitation, wind speed, and direction. In contrast, climate represents the average atmospheric conditions over a defined time span and includes classifications like tropical equatorial, tropical monsoon, and cool temperate climates. Climatic hazards and extreme weather events includes heat waves, droughts, floods, cyclones, and wildfires, all of which have substantial impacts on both natural and human systems.

Why does air temperature vary across Earth’s surface?

Earth's rotation on its axis leads to daily variations in air temperature, while its revolution around the sun causes yearly fluctuations. Globally, solar angles are lower at higher latitudes due to Earth's tilt, resulting in lower air temperatures. Locally, higher altitudes experience lower air temperatures as air pressure decreases. The nature of surfaces, such as snow cover, vegetation, and exposed soil, influences site-specific air temperatures, while coastal areas are affected by the maritime effect and inland areas by continentality, both impacting local air temperatures.

Why does precipitation vary across Earth’s surface?

The water cycle involves the movement of water between the atmosphere and Earth's surface through processes like evapotranspiration, condensation, and precipitation, with water moving at varying rates through infiltration, surface runoff, and groundwater flow. Relative humidity influences condensation, occurring when the amount of water vapour surpasses the atmosphere's holding capacity at a given temperature. Cloud formation is driven by condensation nuclei and the coalescence of water droplets in the atmosphere, leading to precipitation, including convectional and relief rainfall.

Convectional rainfall

Relief rainfall

Why does wind direction and wind speed vary across Earth’s surface?

Wind speed is influenced by the strength of the pressure gradient between two locations and friction resulting from Earth's topography. On a local scale, land and sea breezes occur, while on a regional scale, Northeast and Southwest monsoons are influenced by the Coriolis force. These factors contribute to the complex patterns and variations in wind at different geographic scales.

2. climate change

What is the natural variability of climate?

Evidence of past climates is revealed through geological data, including episodes of cooling and warming over time, as seen in seafloor sediment and oxygen isotope records. Changing climate zones are indicated primarily by temperature, evidenced by the expansion and contraction of main climatic zones. Climate variability is due to natural processes such as changes in Earth's orbit and tilt angle, as well as occurrences of sunspots and large-scale volcanic eruptions.

How do anthropogenic factors contribute to climate change?

The growth in population and industrialization has led to changes in the quantity of greenhouse gases in the atmosphere, specifically carbon dioxide, methane, and nitrous oxide. Recent data indicates successive decades being warmer than any since 1850. The greenhouse effect, a natural process crucial for Earth's habitability, involves the absorption and emission of shortwave and longwave radiation. However, the enhanced greenhouse effect is attributed to human activities, particularly the burning of fossil fuels and changes in land use. These factors contribute to climate change.

How might climate change affect natural systems?

Climate change is affecting natural systems with increased ocean surface temperatures and alterations to ocean circulations, along with rising atmospheric temperatures and shifts in land precipitation patterns. Aquatic ecosystems face threats to coral reefs, disruptions to marine food webs, and the phenomenon of ocean acidification. Terrestrial ecosystems experience risks to flora and fauna, coupled with changes in extreme weather events, including droughts and excessive rainfall. These impacts collectively highlight the broad and interconnected consequences of climate change on both aquatic and terrestrial environments.

How might climate change affect human systems?

The impact of climate change on human systems is geographically uneven, influenced by climate variables and localized economic and social factors. These impacts are interconnected, cascading from natural systems to people. Direct effects of climate change on human systems result from extreme weather events like heat waves, droughts, floods, cyclones, and wildfires. Indirect impacts affect provisioning ecosystem services, including food production, and regulating ecosystem services, such as disease regulation. Additionally, cultural ecosystem services are altered, seen in the melting of Arctic ice and degradation of natural landscapes.

3. climate action

How does climate action help achieve sustainable development?

Climate action involves both adaptation and mitigation strategies, which are complementary responses to the challenges posed by climate change. These actions may generate both risks and benefits. Climate change acts as a threat multiplier, exacerbating other threats to natural and human systems, leading to uneven climate-related effects. Moreover, climate change constrains development paths, with global impacts being uneven and placing additional burdens on disadvantaged communities and developing countries.

Why do climate risks vary across places?

Climate risks arise from the interaction between climate-related hazards and the vulnerability and exposure of natural and human systems to these hazards, potentially resulting in the loss of human lives and property damage. These risks are influenced by both shorter-term events such as cyclones and floods, as well as longer-term events like sea level rise and droughts. Vulnerability and exposure play crucial roles, with vulnerability reflecting the susceptibility of a community's access to water, food, and health resources, and exposure representing the likelihood of natural systems facing extreme weather and environmental degradation. Factors such as proximity to coastal and dry environments contribute to exposure to hazard areas.

How effective are mitigation strategies in building community resilience to climate change?

Mitigation strategies involve altering energy and land use practices. However, their effectiveness is constrained by technological, economic, social, and institutional challenges. Strategies to reduce greenhouse gas emissions include international agreements, cooperation, adoption of low-carbon technologies, utilization of clean energy sources, and shifts in consumption patterns. Additionally, enhancing carbon sinks is achieved through the protection of oceans and forests, as well as the management of land-use changes and forest regeneration.

How effective are adaptation strategies in building community resilience to climate change?

Adaptation strategies aim to minimize the harm caused by climate change, but their effectiveness is constrained by technological, economic, social, and institutional challenges. Strategies involving structural and technological approaches focus on areas such as water and flood management, as well as the use of technology in food production. Social and institutional approaches to adaptation include raising awareness and education, along with the development and implementation of national and regional policies and plans.

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