How Do We Know Climate Change is Real?
KEY TAKEAWAYS
- While Earth’s climate has changed throughout its history, the current warming is happening at a rate not seen in the past 10,000 years.
- According to the Intergovernmental Panel on Climate Change (IPCC), “Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact.”
- Scientific information taken from natural sources (such as ice cores, rocks, and tree rings) and from modern equipment (like satellites and instruments) all show the signs of a changing climate.
- From global temperature rise to melting ice sheets, the evidence of a warming planet abounds.
The rate of change since the mid-20th century is unprecedented over millennia.
Earth’s climate has changed throughout history. Just in the last 800,000 years, there have been eight cycles of ice ages and warmer periods, with the end of the last ice age about 11,700 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.
This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric CO2 has increased since the Industrial Revolution. (Credit: Luthi, D., et al.. 2008; Etheridge, D.M., et al. 2010; Vostok ice core data/J.R. Petit et al.; NOAA Mauna Loa CO2 record.) Find out more about ice cores (external site).
The current warming trend is different because it is clearly the result of human activities since the mid-1800s, and is proceeding at a rate not seen over many recent millennia. It is undeniable that human activities have produced the atmospheric gases that have trapped more of the Sun’s energy in the Earth system. This extra energy has warmed the atmosphere, ocean, and land, and widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.
Earth-orbiting satellites and new technologies have helped scientists see the big picture, collecting many different types of information about our planet and its climate all over the world. These data, collected over many years, reveal the signs and patterns of a changing climate.
Scientists demonstrated the heat-trapping nature of carbon dioxide and other gases in the mid-19th century. Many of the science instruments NASA uses to study our climate focus on how these gases affect the movement of infrared radiation through the atmosphere. From the measured impacts of increases in these gases, there is no question that increased greenhouse gas levels warm Earth in response.
Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly 10 times faster than the average rate of warming after an ice age. Carbon dioxide from human activities is increasing about 250 times faster than it did from natural sources after the last Ice Age.
The Evidence for Rapid Climate Change Is Compelling
Global Temperature Is Rising
The planet’s average surface temperature has risen about 2 degrees Fahrenheit (1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide emissions into the atmosphere and other human activities. Most of the warming occurred in the past 40 years, with the seven most recent years being the warmest. The years 2016 and 2020 are tied for the warmest year on record.
The Ocean Is Getting Warmer
The ocean has absorbed much of this increased heat, with the top 100 meters (about 328 feet) of ocean showing warming of 0.67 degrees Fahrenheit (0.33 degrees Celsius) since 1969. Earth stores 90% of the extra energy in the ocean.
The Ice Sheets Are Shrinking
The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA’s Gravity Recovery and Climate Experiment show Greenland lost an average of 279 billion tons of ice per year between 1993 and 2019, while Antarctica lost about 148 billion tons of ice per year.
Glaciers Are Retreating
Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska, and Africa.
Snow Cover Is Decreasing
Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and the snow is melting earlier.
Sea Level Is Rising
Global sea level rose about 8 inches (20 centimeters) in the last century. The rate in the last two decades, however, is nearly double that of the last century and accelerating slightly every year.
Arctic Sea Ice Is Declining
Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades.
Extreme Events Are Increasing in Frequency
The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events.
Ocean Acidification Is Increasing
Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30%. This increase is due to humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the ocean. The ocean has absorbed between 20% and 30% of total anthropogenic carbon dioxide emissions in recent decades (7.2 to 10.8 billion metric tons per year).
The Causes of Climate Change
KEY TAKEAWAYS
- The greenhouse effect is essential to life on Earth, but human-made emissions in the atmosphere are trapping and slowing heat loss to space.
- Five key greenhouse gases are carbon dioxide, nitrous oxide, methane, chlorofluorocarbons, and water vapor.
- While the Sun has played a role in past climate changes, the evidence shows the current warming cannot be explained by the Sun.
Increasing Greenhouses Gases Are Warming the Planet
Scientists attribute the global warming trend observed since the mid-20th century to the human expansion of the “greenhouse effect” — warming that results when the atmosphere traps heat radiating from Earth toward space.
Life on Earth depends on energy coming from the Sun. About half the light energy reaching Earth’s atmosphere passes through the air and clouds to the surface, where it is absorbed and radiated in the form of infrared heat. About 90% of this heat is then absorbed by greenhouse gases and re-radiated, slowing heat loss to space.
Human Activity Is the Cause of Increased Greenhouse Gas Concentrations
Over the last century, burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2). This increase happens because the coal or oil burning process combines carbon with oxygen in the air to make CO2. To a lesser extent, clearing of land for agriculture, industry, and other human activities has increased concentrations of greenhouse gases.
How do we know what greenhouse gas and temperature levels were in the distant past?
The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels by nearly 50% since 1750. This increase is due to human activities, because scientists can see a distinctive isotopic fingerprint in the atmosphere.
In its Sixth Assessment Report, the Intergovernmental Panel on Climate Change, composed of scientific experts from countries all over the world, concluded thatit is unequivocal that the increase of CO2, methane, and nitrous oxide in the atmosphere over the industrial era is the result of human activities and that human influence is the principal driver of many changes observed across the atmosphere, ocean, cryosphere and biosphere.
Evidence Shows That Current Global Warming Cannot Be Explained by Solar Irradiance
Scientists use a metric called Total Solar Irradiance (TSI) to measure the changes in energy the Earth receives from the Sun. TSI incorporates the 11-year solar cycle and solar flares/storms from the Sun’s surface.
Studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity coupled with increased volcanic activity helped trigger the Little Ice Age.
The above graph compares global surface temperature changes (red line) and the Sun’s energy that Earth receives (yellow line) in watts (units of energy) per square meter since 1880. The lighter/thinner lines show the yearly levels while the heavier/thicker lines show the 11-year average trends. Eleven-year averages are used to reduce the year-to-year natural noise in the data, making the underlying trends more obvious.
The amount of solar energy that Earth receives has followed the Sun’s natural 11-year cycle of small ups and downs with no net increase since 1880. Over the same period, global temperature has risen markedly. It is therefore extremely unlikely that the Sun has caused the observed global temperature warming trend over the past half-century. Credit: NASA/JPL-Caltech
Future Effects of Global Climate Change
Climate Changes Will Continue Through This Century and Beyond
Global climate is projected to continue warming over this century and beyond. The degree of climate change and severity of impacts ultimately depend on the amount of heat-trapping gases emitted by humans and how sensitive Earth’s climate is to those emissions.
Hurricanes Will Become Stronger and More Intense
Scientists project that hurricane-associated storm intensity and rainfall rates will increase as the climate continues to warm. Moreover, as sea level continues to rise, the severity of storm surges will escalate, exacerbating flooding caused by heavy rainfall, leading to heightened damage.
More Droughts and Heat Waves
According to the most recent National Climate Assessment, droughts in the Southwest and heat waves (periods of abnormally hot weather lasting days to weeks) are projected to become more intense, and cold waves less intense and less frequent.
All seasons are projected to continue to get hotter. By the end of this century, if we continue emitting greenhouse gases at our current rate, extreme heat events that used to occur only once in 20 years are expected to occur every year.
Longer Wildfire Seasons
Globally, fire weather seasons have lengthened. Drought remains the dominant driver of fire emissions, but recently there has been increased fire activity in some tropical and temperate regions due to warmer temperatures that increase vegetation flammability. The northern boreal zone (Earth’s northernmost forests) near the Arctic is also experiencing larger and more frequent fires, and this may increase under a warmer climate.
More fires and and an extended fire season are causing an additional health hazards caused by wildfire smoke, impacting tens of millions of people around the world. Simultaneously, the costs associated with fighting wildfires have increased by an astounding 11-fold over the past 30 years, placing an additional financial burden alongside the public health risk.
Changes in Precipitation Patterns
Climate change is having an uneven effect on precipitation (rain and snow) around the world, with some locations experiencing increased precipitation and flooding, while others experience drought. Scientists project more winter and spring precipitation for the northern territories, and less for the southern, over this century.
Projections of future climate suggest that the recent trend toward increased heavy precipitation events will continue. This means that while it may rain less frequently in some regions, when it does rain, heavy downpours will be more common.
Global Temperatures Will Continue to Rise
The climate of the United Kingdom is directly linked to the changing global climate. The last eight years have been the hottest years on record for the globe. Recent research shows that current global temperatures and the rate of the current warming are both unprecedented over the past 24,000 years. These trends are expected to continue, but reducing greenhouse gas emissions would lessen the amount of warming in the future.
Arctic Is Very Likely to Become Ice-Free
Sea ice cover in the Arctic Ocean is expected to continue decreasing, and the Arctic Ocean will very likely become essentially ice-free in late summer if current projections hold. This change is expected to occur before mid-century.
Sustainability and Resources
The Council is deeply committed to sustainability and environmental stewardship within our community. We recognise the urgent need to protect our environment for present and future generations. Inspired by global efforts and best practices, we are developing a comprehensive sustainability policy to guide our actions and ensure responsible environmental management.
Our sustainability policy aims to promote sustainable practices across all aspects of our operations, focusing on minimising our ecological footprint and preserving our natural resources. By integrating sustainability into our daily work, we strive to contribute to the collective efforts in addressing climate change and creating a more sustainable future for our community.
Key Objectives of the Council’s Sustainability Policy:
- Energy Efficiency: We will prioritise energy efficiency measures, aiming to reduce energy consumption and promote the use of renewable energy sources wherever feasible.
- Greenhouse Gas Emissions: We are committed to measuring, monitoring, and reducing both direct and indirect greenhouse gas emissions associated with our activities. Our goal is to minimise our carbon footprint and contribute to global efforts in mitigating climate change.
- Water Conservation: We will implement water conservation measures, including efficient water management, reuse practices, and stormwater management strategies, to protect and preserve our local water resources.
- Waste Reduction and Recycling: We will actively work towards minimising waste generation, preventing pollution, and increasing recycling rates. Our focus will be on promoting responsible waste management practices and raising awareness among our community members.
- Sustainable Procurement: We will prioritise the procurement of sustainable technologies, environmentally preferable materials, products, and services.
- Sustainable Infrastructure: We will promote the design, construction, maintenance, and operation of sustainable buildings and infrastructure within our parish. Our aim is to minimise environmental impact while enhancing the liveability of our community.
- Resource Management: We will explore opportunities for efficient resource management, including power management options. We strive to optimise resource allocation and minimise waste.
- Community Engagement: We are dedicated to engaging and involving our community in sustainable practices. We will foster collaboration, raise awareness, and empower our residents to embrace sustainability in their daily lives.
- Climate Change Resilience: We will assess our vulnerabilities to climate change risks and develop appropriate measures to mitigate and adapt to the impacts. Our goal is to enhance the resilience of our community and safeguard our operations and mission against climate-related challenges.
- Individual Responsibility: We encourage every member of our council, staff, and community to embrace the principles of sustainability in their daily work and personal lives. Together, we can make a significant impact through individual actions.
- Compliance and Accountability: We are committed to complying with all applicable environmental laws, regulations, and standards. We will uphold our responsibility to maintain a healthy environment and conduct our operations in an environmentally sound manner.
The Council is determined to be a leader in sustainability and environmental stewardship. By implementing this comprehensive sustainability policy, we aim to create a resilient and sustainable community that values and protects our natural heritage. We invite all residents, businesses, and stakeholders to join us on this journey towards a greener, more sustainable future. Together, we can make a positive and lasting impact on our environment and the well-being of our community.
For information on the Devon Climate Emergency, visit: