Impact on Climate Chapter Notes | Science for Grade 6 PDF Download

Introduction

The chapter "Impact on Climate" explains how Earth's climate is changing and how human activities are affecting it. Climate is the average weather over a long time, and it can change due to natural events or human actions. This chapter explores why global temperatures are rising, how greenhouse gases play a role, and how these changes affect Earth's ice, oceans, and ecosystems. It also discusses what humans can do to reduce or adapt to these changes, helping us understand our planet better and how to protect it.

What is climate change?

• Climate is the long-term average of weather conditions, like temperature and rainfall.
• Earth’s climate has been changing for 4.6 billion years, over short and long periods.
• Climate change includes changes in temperature, rainfall, wind patterns, and other weather factors.
• Global warming is when Earth’s average surface temperature rises and is a part of climate change.
• Climate change and global warming are not the same, but global warming is one effect of climate change.
• Scientists agree that Earth’s climate is changing, but people disagree on what to do about it.

What do temperature records show?

• Thermometers have measured air temperatures for the last 150 years.
• Temperature records show that Earth is getting warmer over time.

Scientific Consensus

• Climate scientists study why Earth’s temperature is rising.
• Research shows that the increase in temperature is caused by more greenhouse gases in the atmosphere.

What are greenhouse gases and how do they affect climate?

• Greenhouse gases are gases in the atmosphere that trap heat from the Sun.
• Important greenhouse gases include carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O).
• Levels of CO₂, CH₄, and N₂O in the atmosphere have increased a lot in the last 100 years.

Greenhouse Effect

• The greenhouse effect is a natural process where gases in the atmosphere trap heat from the Sun.
• This trapped heat warms Earth’s surface, making it suitable for life.
• Without the greenhouse effect, Earth would be too cold for most living things.
• Higher levels of greenhouse gases trap more heat, causing Earth’s temperature to rise.
• This increase in trapped heat leads to global warming.
• Carbon dioxide (CO₂) is the most important greenhouse gas for climate change.

Where is all of the CO₂ coming from?

• Natural sources like volcanic eruptions, forest fires, and cellular respiration release CO₂ into the atmosphere.
• These natural sources alone cannot explain the high levels of CO₂ we see today.
• Atmospheric CO₂ is at its highest level in at least 800,000 years.
• Human activities, especially burning fossil fuels, are the main source of extra CO₂.
• Deforestation and land use changes are the second biggest source of human-produced CO₂.

Human Impact

• 97% of climate scientists agree that humans are causing climate change.
• The National Oceanic and Atmospheric Association (NOAA) says natural factors would have caused slight cooling over the last 50 years without human activities.
• The Intergovernmental Panel on Climate Change (IPCC) says it is extremely likely that human activities cause the rise in CO₂ and climate change.
• Burning fossil fuels is the largest source of human-produced CO₂.
• Deforestation and land use changes also add a lot of CO₂ to the atmosphere.

How is the recent warming trend affecting earth’s ice?

• Global warming is causing glaciers and ice sheets to melt around the world.
• Since 1980, glaciers with long records have lost ice equal to 15.1 meters (50 feet) of water.
• Glacier National Park had 150 glaciers in 1910, but now has fewer than 30.
• Ice sheets are large glaciers that spread over land in all directions, like in Greenland and Antarctica.
• Greenland’s ice sheet is losing about 286 billion metric tons of ice per year.
• Ice mass loss in Greenland and Antarctica has sped up since 2009.
• Sea ice in the Arctic Ocean is shrinking, reflecting less sunlight and absorbing more heat.
• Less sea ice causes more warming, which leads to even more ice melting.

How is climate change affecting earth’s oceans?

• Oceans absorb heat and CO₂ from the atmosphere.
• Rising global temperatures and CO₂ levels are affecting oceans in many ways.
• Sea levels are rising because of thermal expansion (water expands when it warms) and melting glaciers.
• Rising sea levels erode beaches, wetlands, and can flood low-lying areas.
• About 600 million people live in low-lying coastal areas at risk of flooding.
• Coastal flooding can harm ecosystems and human communities.

Rising Seas

• Thermal expansion and melting ice from glaciers and ice sheets cause sea levels to rise.
• Sea level rise threatens coastal areas, including beaches, wetlands, and cities.
• Flooding from rising seas is a concern for millions of people living near coasts.

Ocean pH

• The absorption of carbon dioxide (CO₂) is causing the oceans to become more acidic.
• Many marine organisms rely on calcium from seawater to build their shells and skeletons.
• As acidity increases, it becomes more difficult for organisms to absorb calcium.
• Weaker or dissolving shells and skeletons result from this increased acidity.
• This change can lead to a decline in marine biodiversity and a reduction in important marine resources.

Oceans on the Rise—Again

• Earth has experienced many long-term warming and cooling periods throughout its history.
• During cooling periods, much of Earth was covered with ice sheets and glaciers.
• In warming periods, ice melted, and sea levels were higher than today.
• About 10% of Earth’s land mass is covered with ice sheets and glaciers now.
• One large ice sheet covers Greenland, and another covers Antarctica.
• Global warming from human activities is melting ice sheets quickly, raising sea levels.
• Ocean warming causes water to expand, adding to sea level rise.
• If ice sheets continue melting at the current rate, sea levels could rise by 1.8–2.4 meters (6–8 feet) by 2100.
• This rise could flood large cities and coastal habitats with about 2100 cubic kilometers of water every year.
• Geologist Daniel Muhs studies rock layers for clues about past sea levels.
• He found a fossilized coral reef in a limestone wall in the Florida Keys.
• The wall is several meters above sea level now but was underwater 125,000 years ago.
• Muhs estimates sea levels were 6–8 meters (18–24 feet) higher then, when Earth was 2°C warmer.
• Sea levels were once several meters higher than they are today.
• Faster warming now could cause sea levels to rise more quickly than in the past.

Did You Know?

• Warming oceans do more than just raise sea levels—they also harm marine life. Corals, for example, are extremely sensitive to even small temperature changes. An increase of just 1°C can cause corals to lose their vibrant color in a process called coral bleaching. This happens when stressed corals expel the algae living inside them. These algae are vital because they give corals both energy and nutrients. When corals die from bleaching, entire habitats for fish and many other sea creatures are destroyed.
• Along with rising temperatures and sea levels, the oceans are also becoming more acidic. This happens because carbon dioxide (CO₂) from the atmosphere dissolves into seawater. As more CO₂ enters the air, more of it ends up in the ocean. When CO₂ mixes with seawater, it forms a weak acid called carbonic acid. This acid lowers the pH of the water, making it slightly more acidic and affecting marine life and ecosystems.

What does a warming climate mean for ecosystems on land?

• A warming climate can cause major shifts in the geographic distribution of organisms.
• As temperatures rise, species that were once limited to warmer regions may begin to spread toward the poles.
• This movement can lead to changes in ecosystems, as new species enter areas where they previously could not survive.

Shifting Ecosystems

• Climate change affects where plants and animals live.
• As climates warm, animals and plants move to new areas, often toward the poles.
• In Europe and North America, 57 butterfly species have moved north or died out in southern areas.
• Plants are also moving to new areas, but some cannot move fast enough to keep up with climate change.
• Trees like oaks move slowly, about a few hundred meters per year, much slower than the changing climate.
• Insect pests and diseases, like mosquitoes, are spreading to new areas as winters get milder.
• Warmer climates help mosquitoes survive in places that were once too cold.
• More mosquitoes can spread diseases, but they also provide food for some animals.

What can be done?

• Understanding climate change helps us find ways to reduce its impact.
• Mitigation strategies slow down climate change by reducing greenhouse gases.
• Adaptation strategies help humans adjust to the effects of climate change.

Addressing Climate Change

• Reducing climate change is challenging but possible with action from individuals and society.
• Ways to reduce climate change include:
  • International agreements like the Kyoto Protocol and Paris Agreement to limit greenhouse gases.
  • Using alternative energy sources like wind, solar, hydroelectric, geothermal, and nuclear power.
  • Conserving energy by using less and improving efficiency of energy systems.
  • Capturing and storing carbon (carbon sequestration).
  • Increasing natural carbon sinks through forest management and conservation tillage.

Adapting to climate change

• It may take 100 years or more to see the effects of actions taken today.
• Societies must adapt to warmer climates while working to reduce climate change.
• Examples of adaptation:
  • In France, farmers plant crops that can handle warmer temperatures.
  • In Austria, ski resorts plan hiking trails and golf courses for a future with less snow.
  • In Copenhagen, Denmark, new subways are built higher to prepare for rising sea levels.