Climate is the average of weather, the way weather usually is over a long time. Scientists who study climate are called climatologists. Climatologists put climates into four groups: warm and wet, warm and dry, cold and wet, cold and dry.
Near the north and south poles the climate is cold. At the equator, the climate is warm. Halfway in between, people live with four seasons where each season has its own climate. Climate is how warm or wet a region is, or isn’t. Deserts have dry climates. Glaciers are in cold climates. Rain forests are wet in wet climates. It doesn't mean that every day the weather is like that, climate tells us that most of the time the weather is like that. Wet climates are in parts of the world near oceans. Cities on a coastline can have wet climates too if wind blows from the water to the land. The wind carries water vapor and clouds from the ocean to drop rain or snow to make the land wet. Dry climates are found where mountains block rain or snow from getting there, or where the wind can’t carry enough moisture.
The sun’s energy creates warm climates near the equator, where the sun is high in the sky, and the rays are strong all year. When you go toward the North or South Pole the climate is colder. That's because the sun stays lower in the sky and those parts of Earth don't get as much energy from it. Air with water vapor and clouds, keeps the planet from cooling down too much. It helps to keep the entire planet at a steady temperature. Without air, the Earth would be too cold for people, animals, and plants to live. The air for the planet acts the way a blanket does on you, while you sleep. It holds in heat. This is sort of what happens in a greenhouse. Clear plastic or glass helps to trap heat inside so that when the sun goes down, or in the colder seasons, the greenhouse stays warm. Climatologists are very concerned that if we keep polluting the air by adding gasses like carbon dioxide and methane from fossil fuels, that air will trap more heat to warm the Earth. A warmer planet creates climate change.
In our current climate change, air, land, and oceans warm, mostly due to human activities. More water evaporates into the air. More water vapor in air also warms the planet, while making heavier rain in some places. At the same time, changes in wind around the globe could cause other places and cities to become drier. Oceans will continue to rise so people along coastlines might have to move, or raise their homes above the ground. Coastlines get more flooding and erosion from storms and from regular high tides. Some animals and people lose their habitats and food sources. Other animals and insects migrate and that can cause problems with humans and our communities.
While change is a normal part of Earth’s history, what makes climate change bad is that most people don’t like change. Our homes and cities are not built to be changed. It will be very expensive for countries, cities, and even for families to make adjustments. A warming Earth melts glaciers. If water resources change, it could become a struggle to get water for agriculture or everyday use. Where water and agriculture shift, millions of people may be displaced and have to migrate. Not all climate change is immediately bad for everybody and everything. Extra carbon dioxide in the air could help more trees and plants to grow, although not enough to stop the change. In cold climates, winters might be shorter and not as much snow would fall. That would make transportation easier. Some deserts and dry places might become wet enough for farmers to grow food and for people to live there. If ocean ice continues to melt near the Arctic, it would make shipping routes shorter. Unfortunately, most of what happens as the Earth warms is not good for how animals and people live.
While oceans do a great job of storing carbon dioxide and heat, those things are not good for coral and other sea creatures. Scientists do not know how much carbon dioxide the oceans can store. Newer satellites carry instruments to give us weather readings and water temperature. Ocean buoys use thermometers to measure how warm the water is, and they provide wind and humidity data. Scientists use underwater drones to see how heat and carbon dioxide move around in the seas. Putting all the data together, a climatologist can create computer models that project how climate may change as the globe warms. While Earth’s climate has been warmer than what it is now, climatologists know that it has not been as warm as it is now since humans have been on the planet. More important is that the speed of climate change has never been this fast before. There has never been as much Carbon Dioxide from fossil fuels in the air as there is now.
One of the tricky things about a warming planet is that a big volcano can erupt and change climate for a short while, by sending ash and smoke into the air. Wind could carry it around the Earth to make a shield, blocking some sunlight and making the Earth colder. That would not stop global warming. Another tricky thing about a warmer planet, is that sea level could actually lower along coasts where changing ocean currents carry colder, more dense water to the shore. Some spots that don’t get a lot of snow now, could actually get more snow if the moisture in air increases and the temperature doesn’t.
Climate scientists believe the main cause of rising seas and a warming planet are the result of the pollution we put into the air. Cars, trucks, buses, ships, and factories all make pollution when they burn oil, gas, or coal. These are called fossil fuels. Just think of how much gasoline people put in their cars. When the engine burns it, the liquid fuel becomes an invisible gas. Whenever we burn fossil fuels, they give off carbon dioxide and sometimes methane. While carbon dioxide has always been on Earth, and is good for trees and plants, too much of it is a problem because it traps heat on Earth. Many climatologists predict that if we don't reduce adding carbon dioxide and pollution to air that climate change will happen faster. Nobody knows for sure how fast and for how long the planet will keep on warming, but just to be safe, there are basic things you can do to help slow down climate change.
In a changing climate, there will always be regular weather. There will still be record cold, and record snow, That doesn’t mean we are not warming up. We know we are, from measurements, and from clues about how our global climates used to be. We know that in our cities, the air is also warmer because of the pavement, buildings, traffic, and because there are fewer trees to absorb heat and create shade.
Scientists drill deep holes in glaciers and pull out cores of ice. If they drill far enough in large glaciers, they can find little bubbles of air that were trapped in the ice a million years ago. The air in those bubbles tells exactly how much carbon dioxide and other gasses there were.
Glaciers sit on land in very cold regions and grow faster than they melt. Glaciers move downhill but it’s so slow that it’s hard to notice. When glaciers reach a lake or ocean, they break into pieces and float as ice or icebergs. There is more fresh water locked up in the ice of glaciers than you find in all of the lakes of the world. But it is still a small amount. If all of the water on Earth were put into 100 large buckets, only 2 of the buckets would hold the water from melted glaciers.
Even in the mud of lakes and oceans, there are clues in the sediment and in old shells of sea life as to how warm things were millions of years ago, and how much carbon dioxide was in the air. When large old trees are cut down, the tree rings show how much and how fast the trees grew. This tells us if some years were warm and if some were wet. A climate scientist can get even more climate history from petrified trees, going back millions of years.
Weather patterns shift when climate shifts or they shift temporarily in different seasons. There are some shifts in weather patterns that don’t happen on a regular cycle. One that we know a lot about is called El Niño. El Niño is when the water in the eastern and middle of the Pacific Ocean gets much warmer than usual for many months. Because there’s so much water there, a small change in the ocean temperature can change winds around other parts of the Earth and make a big difference in weather patterns in some regions. It’s called El Niño because it is something that is often noticed around the coast of Central America around Christmas, and El Niño is Spanish for the Christ Child.
When there is an El Niño, some countries and regions get weather that is stormier or wetter. Other areas get weather that is drier and calmer. Dry weather is bad for farmers and bad for ski resorts because they don't get a lot of snow, but dry weather is good for construction workers outdoors, or for people who just want to play sports outside. Even in a single country, parts of it might be wetter while other parts would be warmer. Wet is not good if you want to go outside but it is good for trees to grow. Warmer is not good when there are wildfires, but warmer is good in the winter, unless you want to ski. One of the best things about El Niño’s is they often lower the number of hurricanes in the Atlantic Ocean.
La Niña is the opposite of El Niño. That's when the eastern and central Pacific Ocean gets colder than usual. La Niña also changes weather in regions around the world. El Niño and La Niña are part of climate because they can last for many months or for years. When the temperature of the central Pacific Ocean changes, weather patterns shift but it's not always a bad thing for everyone. Whenever there's bad weather someplace, there's usually good weather somewhere else.