11.1 Global temperature trends and patterns
2 min read•july 22, 2024
Global temperatures have risen significantly since pre-industrial times, with the past five years being the warmest on record. This warming trend, driven mainly by human activities, shows distinct patterns across the Earth's surface, with land warming faster than oceans.
The causes of temperature change include both natural variability and human factors. While short-term fluctuations can be attributed to events like , the long-term warming trend is primarily due to increased greenhouse gas emissions from human activities.
Global Temperature Trends and Patterns
Global temperature trends
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- increased by approximately 1.0°C (1.8°F) since pre-industrial times
- Warming accelerated in recent decades with warmest years on record occurring in the 21st century (2016, 2020)
- Rate of warming approximately 0.2°C (0.36°F) per decade since 1981
- Past five years (2016-2020) warmest on record with 2020 tying with 2016 for warmest year
Spatial patterns of warming
- Land surfaces warmed faster than ocean surfaces
- Land has lower heat capacity than water allowing it to warm and cool more rapidly
- Oceans absorb more heat and distribute it through currents and mixing
- Polar regions (Arctic, Antarctic) experienced amplified warming compared to global average
- Arctic warming more pronounced than Antarctic warming
- Factors contributing to include:
- : As ice and snow melt, surface becomes darker and absorbs more solar radiation
- Changes in atmospheric and oceanic circulation patterns
- Increased heat transport from lower latitudes to poles
Causes of temperature change
- Natural variability (El Niño, , volcanic eruptions, solar activity) can influence global temperatures on short timescales
- El Niño events tend to increase global temperatures while La Niña events have cooling effect
- Large volcanic eruptions can temporarily cool Earth by injecting sulfate aerosols into stratosphere which reflect incoming solar radiation
- Anthropogenic factors, primarily greenhouse gas emissions from human activities, are dominant cause of observed warming trend
- Greenhouse gases (, , ) trap heat in atmosphere
- Burning of fossil fuels, deforestation, and industrial processes increased atmospheric concentrations by over 40% since pre-industrial times
- Other anthropogenic factors include land-use changes and aerosol emissions
Analysis of temperature data
- Global temperature datasets (NASA, NOAA, UK Met Office) provide instrumental records of temperature changes over time
- Datasets derived from land-based weather stations, ships, buoys, and satellites
- Data quality-controlled and adjusted for factors such as urbanization and changes in measurement techniques
- represent deviations from long-term average
- Anomalies help remove effects of natural spatial variability and highlight long-term trends
- Maps and animations visualize spatial patterns of temperature change (land-ocean contrasts, polar amplification)
- Time series plots and trend lines illustrate long-term global temperature trends and acceleration of warming in recent decades
Key Terms to Review (20)
Average global temperature: Average global temperature refers to the mean temperature of Earth's atmosphere and oceans, which is calculated based on temperature measurements taken at various locations around the globe. This metric is crucial for understanding climate trends and assessing the impacts of climate change, as it provides a comprehensive view of how global temperatures fluctuate over time due to natural and anthropogenic influences.
Climate feedbacks: Climate feedbacks are processes that can amplify or dampen the effects of climate change, influencing the Earth's temperature and climate system. These feedbacks can either be positive, which enhance warming, or negative, which counteract it, and they play a crucial role in shaping future climate scenarios, temperature trends, historical events, atmosphere-ocean interactions, and greenhouse gas dynamics.
Climate models: Climate models are mathematical representations of the Earth's climate system that use physical principles to simulate and predict climate behavior over time. They help scientists understand how various factors, such as greenhouse gas emissions, land use, and solar radiation, influence climate patterns, aiding in the evaluation of future climate scenarios and their potential impacts.
El Niño: El Niño is a climate pattern characterized by the periodic warming of sea surface temperatures in the central and eastern Pacific Ocean, significantly influencing global weather and climate. This phenomenon can disrupt normal weather patterns, leading to changes in precipitation, temperature, and storm activity around the world.
Global average surface temperature: Global average surface temperature refers to the mean temperature of the Earth's surface, including land and ocean temperatures, measured over a specific period. This metric is crucial for understanding climate change and its impacts, as it reflects changes in energy balance and greenhouse gas concentrations in the atmosphere. Variations in this temperature can indicate broader climate trends and patterns, impacting ecosystems, weather systems, and sea level rise.
Global warming: Global warming refers to the long-term increase in Earth's average surface temperature due to human activities, primarily the burning of fossil fuels, which increases concentrations of greenhouse gases in the atmosphere. This rise in temperature impacts climate patterns, causing changes in weather systems, rising sea levels, and disruptions in ecosystems.
Ground-based observations: Ground-based observations refer to the data collection methods that involve monitoring environmental parameters directly from the Earth's surface. These observations are crucial for understanding climate change and global temperature trends, as they provide real-time data on various factors, such as air temperature, humidity, and precipitation patterns. Ground-based observations complement satellite measurements, helping to build a more comprehensive understanding of the Earth's climate system.
Historical climate data: Historical climate data refers to the records and measurements of climate variables, such as temperature, precipitation, and wind patterns, collected over long periods. This data is essential for understanding past climate conditions, trends, and patterns, which can provide insights into current climate changes and future projections. By analyzing historical climate data, scientists can identify variations and anomalies in the Earth's climate system and assess the impacts of natural and human-induced factors on climate over time.
Ice-albedo feedback: Ice-albedo feedback is a climate process where changes in ice cover affect the Earth's surface reflectivity (albedo), which in turn influences temperature and further ice loss. As global temperatures rise, ice melts, reducing the albedo effect because darker ocean or land surfaces absorb more sunlight, leading to increased warming and more ice melt, creating a self-reinforcing cycle that has significant implications for climate change.
James Hansen: James Hansen is a prominent American climate scientist known for his research on climate change and his role in raising public awareness about global warming. He is particularly recognized for his early warnings regarding the impacts of greenhouse gas emissions, emphasizing the urgency of addressing climate change through policy and action.
Kyoto Protocol: The Kyoto Protocol is an international treaty that commits its parties to reduce greenhouse gas emissions, based on the premise that global warming exists and human-made CO2 emissions have caused it. This agreement reflects the growing acknowledgment of climate change and aims to set legally binding obligations for developed countries to decrease their emissions, thus connecting to broader discussions about climate science, global temperature trends, and greenhouse gas management.
La Niña: La Niña is a climate pattern characterized by cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean, which influences weather patterns across the globe. This phenomenon can lead to significant changes in temperature and precipitation, impacting global climate trends and variability, as well as extreme weather events.
Michael Mann: Michael Mann is a prominent climate scientist known for his research on global warming and climate change. He is widely recognized for his work in developing the 'hockey stick' graph, which illustrates the rapid increase in global temperatures in the 20th century compared to previous centuries. His findings have significantly influenced the understanding of global temperature trends and major climate events throughout Earth's history.
Paris Agreement: The Paris Agreement is a landmark international treaty adopted in 2015 that aims to address climate change by limiting global warming to well below 2 degrees Celsius above pre-industrial levels, while pursuing efforts to limit the temperature increase to 1.5 degrees Celsius. It establishes a framework for countries to set and achieve their own greenhouse gas reduction targets, emphasizing the importance of sustainable development and climate resilience.
Polar Amplification: Polar amplification refers to the phenomenon where the polar regions of the Earth warm at a rate significantly faster than the global average temperature increase. This is mainly due to feedback mechanisms such as melting ice and changing ocean currents, which reduce the albedo effect, allowing more solar energy to be absorbed. As temperatures rise in these regions, it leads to further changes in climate patterns globally.
Radiative forcing: Radiative forcing is a measure of the influence a factor has on the energy balance of the Earth's atmosphere, usually expressed in watts per square meter (W/m²). It quantifies how different factors, such as greenhouse gases or aerosols, affect the balance of incoming solar energy and outgoing infrared radiation, thus playing a critical role in climate change dynamics.
Satellite measurements: Satellite measurements refer to the use of remote sensing technology aboard satellites to collect data about Earth's atmosphere, oceans, land, and ice. This technology enables scientists to monitor changes over time, including variations in global temperatures and sea levels, providing crucial insights into climate change and its impacts on the planet.
Temperature Anomalies: Temperature anomalies refer to the deviations from a long-term average temperature for a specific location and time period. This measurement helps scientists identify trends and patterns in climate change, as it highlights significant fluctuations in temperature over time compared to the established baseline. Understanding temperature anomalies is essential for recognizing global warming impacts and regional climate variations.
Thermal stress: Thermal stress refers to the mechanical stress experienced by materials when they undergo temperature changes, leading to expansion or contraction. This phenomenon is crucial to understanding how climate change impacts various ecosystems, as shifts in global temperatures can create significant stress on natural and human-made systems, affecting their stability and functionality.
Urban heat island effect: The urban heat island effect refers to the phenomenon where urban areas experience significantly warmer temperatures than their rural surroundings, primarily due to human activities and alterations in land cover. This temperature difference is mainly caused by the replacement of vegetation with buildings, roads, and other infrastructure, which absorb and retain heat. The impact of this effect can be seen in global temperature patterns, atmospheric chemistry, and urban planning efforts to create more resilient environments.