Climate is not the same thing as weather. Weather is the minute-by-minute variable condition of the atmosphere on a local scale. Climate is the expected yearly weather conditions established over decades. Jump to Climate is NOT Weather
Search this Site
What You Need to Know About Principle 4: Climate is Variable
This principle relates to some of the differences between weather and climate, how processes like El Nino and the Southern Oscillation influence natural climate variability, and abrupt climate change, which can be triggered by naturally occurring dynamics. Understanding climate variability is critically important in helping scientists tease apart natural variation from human-caused climate change. Click the tabs below to learn more.
Explore this principle by clicking through the bubbles (each takes you to a new concept) at the top of the page.
A Little About What Climate Is
Climate is determined by the long-term pattern of temperature and precipitation averages and extremes at a location.
Climate descriptions can refer to areas that are local, regional, or global in extent and can be described for different time intervals, such as decades, years, seasons, months, or specific dates of the year.
But climate is not weather and the two should never be confused. Climate looks at long-term patterns, weather looks at the short term. Read more…
Average monthly temps
Climate is NOT Weather
Climate is not the same thing as weather.
Weather is the minute-by-minute variable condition of the atmosphere on a local scale.
Climate is the expected yearly weather conditions established over decades. In other words, if you were planning a trip to a faraway place and had no way of knowing what the weather was going to be like, climate is what you would expect to experience based on long-term weather averages for that place. Climate tells you what clothes to buy. Weather tells you what clothes to wear (that day).
For example, the observed weather in Seattle, Washington, on Saturday, October 16, 2010 was sunny with a high of 47°F. But if you were talking about the climate there, you would say: the average high temperature for Seattle, Washington, on October 16 for the period from 1971 to 2000 is 60°F, a value determined by taking the average of all high temperatures recorded for the thirty October 16ths that have occurred over almost 30 years. Read more…
Natural Climate Variability is NOT Climate Change
When scientists talk about climate change, they are talking about a long-term change in an area’s average climate conditions. They are not talking about things like the differences between seasons or cycles like El Niño.
Multi-year, periodic cycles like El Niño produce warm, cool, wet, or dry periods across different regions over one or more years. These are a natural part of the way climate varies and help scientists tell the difference between climate change that is naturally caused and climate change that is human caused, but they do not represent climate change. Read more…
Global Climate has Changed in the Past and Will Change in the Future
Scientific observations show that the earth’s climate has changed in the past, is changing now, and will change in the future.
But the magnitude and direction of that change varies depending on where you are on the planet.
So just as climates across the Earth vary widely, the changes that accompany recent climate change are also varied. Read more…
The Average Temperature is Warmer Now Than it has Been in 1,300 Years
Because records of temperature and precipitation using thermometers, rain gauges and the like have only been used for a few centuries, scientists need some source of reliable climate data before there were thermometers. So scientists use something called a “proxy.”
A proxy is a type of substitute (like a substitute teacher—it’s there when the original can’t be). Fortunately there are lots of climate proxies that allow scientists to extend the study of climate back thousands and even hundreds of thousands of years. Examples include: ice cores, ancient pollen, tree rings, boreholes, corals, lake and ocean sediments, and cave formations.
The Rate of Change is Different Too: NASA says Earth is warming at a pace 'unprecedented in 1,000 years'
NASA says that records of temperature taken via analysis of ice cores and sediments, suggest that the warming of recent decades is out of step with any period over the past millennium. “In the last 30 years we’ve really moved into exceptional territory,” Gavin Schmidt, director of Nasa’s Goddard Institute for Space Studies, said. “It’s unprecedented in 1,000 years. There’s no period that has the trend seen in the 20th century (in terms of how fast temperatures are increasing).”
We Have Known for a Long Time How the Greenhouse Effect Works
A generation after John Tyndall developed the theory and conducted observations that led to the concept of the greenhouse effect, Svante Arrehenius (1859-1927) in Sweden made calculations on the influence of carbon dioxide in the air upon the temperature of the ground. His interest was motivated by the observation that burning coal—which was widespread across Europe—added carbon dioxide (CO2) to the air. His calculations suggested that adding CO2 could cause the planet to warm, in effect amplifying the effect of greenhouse gases already naturally in the atmosphere.
The father of climate change
Ian Sample looks at how the study of the climate has moved from being a relatively minor branch of science to one that now dominates most others, thanks largely to the work of one man
Behind the treelined embankment that borders the campus of Stockholm University lies building 92E, a red brick villa as big as a fire station, its back turned to Roslagsvägen, the main artery linking the capital city with Norrtälje 70km away.
What few markings there are on the building suggest nothing of its history. A sign above the entrance identifies it as Cafe Bojan, a student canteen, and a few shirtless students on a bench in the morning sun recall it as nothing more.
At the end of the 19th century, building 92E was the home and laboratory of Svante Arrhenius, a chemist who became Sweden's first Nobel prizewinner. He was destined to have a bigger impact than he could have imagined, far beyond his mainstream work. Unwittingly, he uncovered secrets of the Earth's atmosphere and in doing so triggered research into what many see as the biggest threat to modern humans. He is arguably the father of climate change science.
That title would be a surprise, even to him. The son of a land surveyor, Arrhenius thrived at school, showing a particular aptitude for arithmetic, but his diversity of thought and penchant for maverick theories dealt him a hefty blow at university. His PhD research, which he began at Uppsala University to the north of Stockholm, focused on the conductivity of electrolytes, but the ideas he put forward in his thesis baffled his professors and he was awarded the lowest possible pass grade. At once, any hopes of staying on at Uppsala were destroyed, and Arrhenius embarked on a tour of European laboratories before landing a job in Stockholm several years later.
Arrhenius became interested in a debate occupying the scientific community, namely the cause of the ice ages. Could it be, he wondered, that vast swings in the levels of atmospheric CO2, lasting tens of millions of years, were the trigger?
The link between CO2 and the Earth's temperature had been made years beforehand. It was the French scientist Joseph Fourier who first realised that certain atmospheric gases shrouded the planet like a bell jar, transparent to sunlight, but absorbing to infrared rays. It means the atmosphere is heated from above and below: first, by sunlight as it shines through and second by the infrared the Earth emits as it cools overnight.
Arrhenius set himself the task of working out just how much water and CO2 in the atmosphere warmed the planet. From others' work, he knew that CO2 was only part of the process. While CO2 and other gases trapped infrared radiation and so heated the atmosphere, warmer air holds more water vapour, itself the most potent contributor to the greenhouse effect. So, if atmospheric CO2 levels increased, water vapour would ensure the warming effect was seriously magnified.
What followed was a year doing what Arrhenius described as "tedious calculations". His starting point was a set of readings taken by US astronomer Samuel Langley, who had tried to work out how much heat the Earth received from the full moon. Arrhenius used the data with figures of global temperatures to work out how much of the incoming radiation was absorbed by CO2 and water vapour, and so heated the atmosphere.
Between 10,000 and 100,000 calculations later, Arrhenius had some rough, but useful, results that he published in 1896. If CO2 levels halved, he concluded, the the Earth's surface temperature would fall by 4-5C. There was a flipside to his calculations: doubling CO2 levels would trigger a rise of about 5-6C.
Beyond the argument over ice ages it wasn't lost on Arrhenius that human activity, in the form of widespread burning of coal, was pumping atmospheric CO2 above the natural levels that help make the Earth habitable. Almost as a passing comment, he estimated that coal burning would drive a steady rise in CO2 levels of about 50% in 3,000 years, a prospect he found entirely rosey. At a lecture that same year, he declared: "We would then have some right to indulge in the pleasant belief that our descendants, albeit after many generations, might live under a milder sky and in less barren surroundings than is our lot at present."
As the first to put hard figures on the greenhouse effect, it's unsurprising Arrhenius's estimates weren't spot on. He thought it would take millenia to see a 50% rise in CO2 - but modern measurements show a 30% rise during the 20th century alone. He thought a doubling of CO2 would raise temperatures by 5-6C. Scientists now say 2-3C is more likely.
Over the next decades, his work was criticised, backed up and criticised again. Many disregarded his conclusions, pointing to his simplification of the climate and how he failed to account for changes in cloud cover and humidity. The oceans would absorb any extra CO2 pumped into the atmosphere, and any remainder would be absorbed by plant life, leading to a more lush landscape, sceptics argued.
In 1938, nine years after Arrhenius had died a Nobel prizewinner for his work on ionic solutions, English engineer Guy Callendar gave the greenhouse theory a boost. An expert on steam technology, he took up meteorology as a sideline and became interested in suggestions of a warming trend. Callendar pieced together temperature measurements from the 19th century onwards and saw an appreciable rise. He went on to check CO2 over the same period and discovered levels had increased about 10% in 100 years. The warming was probably due to the higher levels of CO2.
The existence of an increasing greenhouse effect was hotly debated until the postwar funding of the 1950s kicked in and researchers began to get firm data. In 1956, physicist Gilbert Plass confirmed adding CO2 to the atmosphere would increase infrared radiation absorbed, adding that industrialisation would raise the Earth's temperature by just over 1C per century. By the end of the 1950s, Plass and other scientists in the US started warning government officials that greenhouse warming might become a serious issue in the future.
Unwittingly, the US especially had already started monitoring what many believed were the direct effects of a warming world. Submarines operating in the Arctic Circle took accurate readings of the thickness of the ice sheets above them. When the Pentagon released the data nearly 40 years later, it revealed a startling melting of the ice, on average a 40% thinning of 1.3m since 1953.
In the 1960s, researchers at Scripps Institution of Oceanography in San Diego took on the testing challenge of taking a vast number of measurements of atmospheric CO2. The aim was to establish a baseline level with which future readings in a decade or so could be compared.
Charles Keeling spent two years taking measurements in Antarctica and above the Mauna Loa volcano in Hawaii but reported that even in this short period, CO2 levels had risen. He concluded that the oceans weren't absorbing greenhouse gases being pumped out by industry. Instead, emissions were driving levels of CO2 higher. "It was a seminal discovery. For the first time, scientists knew that the oceans weren't going to absorb all this carbon dioxide," says Mike Hulme at the Tyndall Centre for climate change research at the University of East Anglia.
Still, few saw the greenhouse effect and the warming it would bring as being a problem. At the time, computer models were suggesting modest increases, perhaps 2C in hundreds of years.
By the 1980s, climate change had become a megascience, attracting scientists from diverse fields, each attacking the problem from a different angle. One technique was especially useful. Deep cores of ice cut from Greenland and elsewhere held pockets of air dating back hundreds of thousands of years. By analysing the trapped air, scientists worked out CO2 levels in the atmosphere during past ice ages. In 1987, a core cut from central Antarctica showed that in the previous 400,000 years, CO2 had dropped to 180 parts per million (ppm) during the most extreme glacial periods and climbed as high as 280ppm in warmer times, but not once had been higher. In the outside air, CO2 was measured at 350ppm, unprecedented for nearly half a million years.
To mainstream scientists, evidence that warming was down to human activity was becoming too big to ignore. While scientists uncovered evidence for the greenhouse effect and warming it was producing, others pointed to different processes impacting on global climate. Volcanos, for example, blast millions of tonnes of sulphur dioxide into the atmosphere that form aerosol particles which reflect sunlight back into space. The 1991 eruption of Mount Pinatubo in the Phillipines sent about 20m tonnes of the gas into the atmosphere, leading to a global cooling of around 0.5C a year later. Scientists now believe that the warming experienced in the early 20th century can largely be explained by the lack of volcanic activity.
Variations in the sun's intensity have also been fingered as a driver of climate change. According to Joanna Haigh at Imperial College London, about a third of the warming since 1850 can be explained by solar activity. The identification of disparate contributors to warming has been seized upon by a minority who claim global warming is driven far more by nature than human activity, and the ensuing controversy is still not settled.
By 1988, the United Nations had established the Intergovernmental Panel on Climate Change to review relevant research. The panel's latest estimate points to a warming of 1.4-5.8C by 2100, depending on what strategies, if any, are adopted to curb emissions. The 20th century saw a rise in temperature of 0.6C, about half of which occured since 1970.
Arguably the most concerted effort to cut global emissions has been triggered by the Kyoto Protocol. Since ratification began in 1997, more than 100 countries have adopted the protocol, which for the first time committed them to cutting emissions of six greenhouse gases.
Now, barely a week goes by without a major study on climate change. A flurry of papers started the year with warnings that the Gulf Stream would grind to a halt, ski resorts would move to higher altitudes and Antarctic glaciers were melting fast. More than 100 years after Arrhenius set out to discover why the world fell into periodic ice ages, the scientist has become a pillar of the megascience that is global warming research.
Back in Stockholm' meteorology department, Erland Kallen is musing about progress since Arrhenius first set about his calculations. "Even when I came to this field 20 years ago, I was very sceptical about global warming. There were too many uncertainties I just couldn't see how anyone could say anything sensible about it. Now, I struggle to see what other explanation there could be."
Swedish scientist, Svante Arrherius, puts forward the theory of the greenhouse effect and calculates that doubling of carbon dioxide in the atmosphere will increase temperatures by 5°C to 6°C
US weapons researcher Gilbert Plass pursues climate research in his free time and analyzes how carbon dioxide traps heat. He announces that climate change could be a severe problem to future generations.
The First World Climate Conference, sponsored by the World Meteorological Organization, is held in Geneva, Switzerland. Extremeweather events earlier during the decade had focussed public attention on climate.
Ice cores from the Greenland ice sheet show dramatic temperature oscillations in a single century from the past, an extremely short period for climate change. Scientists also call 1981 the warmest year on record.
The Kyoto Protocol is negotiated to reduce greenhouse gas emissions 5.2% below 1990 levels by 2012 in the developed countries including the former communist bloc.
Kyoto Protocol enters into legal force on Feb 16. The treaty was ratified by more than 140 countries. Concentration of carbon dioxide now stands at 372 parts per million, higher than at any time in at least the past 420,000 years.
Carbon Dioxide Stays in the Atmosphere for a Century or Longer
Natural processes that remove carbon dioxide from the atmosphere operate very slowly compared to the processes that are now adding it to the atmosphere. Thus, carbon dioxide introduced into the atmosphere today will remain there for a century or longer. Other greenhouse gases, including some created by humans, will remain in the atmosphere for thousands of years.
Moving greenhouse gases from the atmosphere into terrestrial and oceanic sinks is a process so slow it is difficult to comprehend. CO2 can be in the atmosphere for thousands of years. The geologic processes trapping atmospheric carbon into sedimentary rocks, like limestone, take hundreds of millions of years. Read more…
click the image to enlarge
The Carbon Cycle
Take a bite of dinner, a breath, or a drive in a car — you are part of the carbon cycle — moving carbon from one reservoir to another.
Source: NOAA (Featured in ESRL's Carbon Cycle Toolkit)
Carbon is the chemical backbone of life on Earth, a key element in many important processes. Carbon compounds help to regulate the Earth’s temperature, make up the food that sustains us, and provide a major source of the energy to fuel our global economy. Most of Earth’s carbon is stored in rocks and sediments, while the rest is located in the ocean, atmosphere, and in living organisms - these are the reservoirs through which carbon cycles.
Carbon moves from one storage reservoir to another through a variety of mechanisms. One example is the movement of carbon through the food chain. Plants move carbon from the atmosphere into the biosphere through photosynthesis: they take in carbon dioxide and use energy from the sun to chemically combine it with hydrogen and oxygen to create sugar molecules. Animals that eat the plant can digest the sugar molecules to get energy for their bodies. Respiration, excretion, and decomposition release the carbon back into the atmosphere or soil continuing the cycle.
The ocean plays a critical role in the storage of carbon, as it holds about 50 times more carbon than the atmosphere. Two-way carbon exchange can occur quickly between the ocean’s surface waters and the atmosphere, but carbon may also be stored for centuries at the deepest ocean depths.
Rocks such as limestone and fossil fuels such as coal and oil are storage reservoirs that contain carbon from plants and animals that lived millions of years ago. When these organisms died, slow geologic processes trapped their carbon and transformed it into these natural resources. Processes such as erosion release this carbon back into the atmosphere very slowly while volcanic activity can release it very quickly. Burning of fossil fuels in cars or power plants is another way this carbon can be released into the atmospheric reservoir quickly.
Changes to the Carbon Cycle
The increasing human population and their activities have a tremendous impact on the carbon cycle. Burning of fossil fuels, changes in land use, and the use of limestone to make concrete all transfer significant quantities of carbon into the atmosphere. As a result the amount of carbon dioxide (CO2) in the atmosphere is rapidly rising and is already significantly greater than at any time in the last 800,000 years. This increase of CO2 is affecting our ocean as it absorbs much of the CO2 that is released from burning fossil fuels. This extra CO2 is lowering the ocean’s pH, this process is called ocean acidification and interferes with the ability of marine organisms (such as corals) to build their shells and skeletons.
A Different Climate, A Different World: During the Last Ice Age, the Pacific Northwest Experienced Enormous Floods
An Introduction to the Ice Age Floods
During the last Ice Age (18,000 to 12,000 years ago), and in multiple previous Ice Ages, cataclysmic floods inundated portions of the Pacific Northwest from Glacial Lake Missoula, pluvial Lake Bonneville, and perhaps from subglacial outbursts. Glacial Lake Missoula was a body of water as large as some of the USA’s Great Lakes. This lake formed from glacial meltwater that was dammed by a lobe of the Canadian ice sheet. Perhaps every 40 to 140 years, the waters of this huge lake forced its way past the ice dam, inundating parts of the Pacific Northwest. Eventually, the ice receded northward far enough that the dam did not reform, and the flooding episodes ceased. These floods are a remarkable part of North American natural heritage. They have profoundly affected the geography and ways of life in the region, but have until recently remained largely unknown to the general public.
The Ice Age Floods Story – Briefly
During the most recent episode of major ice-sheet expansion, between about 18,000 and 13,000 years ago, a lobe of the Cordilleran ice sheet advanced into the Idaho Panhandle to the area that is now occupied by Lake Pend Oreille, thus blocking the Clark Fork River drainage and causing Glacial Lake Missoula to form. At its largest, the lake was deeper than 2,000 feet deep at the dam and held over 500 cubic miles of water—as much as Lake Erie and Lake Ontario combined. The ice dam, however, was subject to repeated failure.
When the dam broke, a towering mass of water and ice was released and swept across parts of Idaho, Washington, and Oregon on its way to the ocean. The peak rate of flow was ten times the combined flow of all the rivers of the world. The huge lake may have emptied in as little as two or three days. Over a period of years the glacier would advance, once again blocking the river, and the dam and the lake would form again. This process was repeated scores of times, until the ice sheet ceased its advance and receded to the north at the end of the Ice Age. It is assumed that the same processes would have occurred earlier during other glacial advances throughout the Ice Age, although most of the evidence for the earlier events may have been removed by the flooding that occurred during the last glacial advance.
Areal Scenario Map of the Ice Age Floods.
Along the floodwaters’ course, more than 50 cubic miles of earth and rock were removed, and some of this was transported and then deposited as new landforms. The floods built gravel bars as tall as 400 feet and moved boulders weighing many tons as if they were pebbles. Some of the eroded material was deposited along the path of the floods, but most of the eroded material was carried out onto the floor of the Pacific Ocean, where extensive deposits of flood sediment have recently been identified hundreds of miles from the current mouth of the Columbia River.
In the following years the account was refined, as evidence of more than one flood was discovered. It is now established that there were large numbers of Ice Age floods that swept across the US Northwest, and some of them were among the largest and most powerful floods that have ever occurred on Earth.
These floods are a remarkable part of North American natural heritage. They have profoundly affected the geography and ways of life in the region, but have until recently remained largely unknown to the general public.
How the “Story” Began
Early settlers in eastern Washington State recognized that the landscapes were different than those seen in other places but were not sure why. A closer examination of the features in the Basin led one geologist, J. Harlen Bretz, to propose that only a sudden cataclysmic flood, on a scale never before considered possible, could account for the phenomenal size and distinctive characteristics of the landforms. This radical idea was not well received by fellow geologists, and a long-running scientific dispute followed. Ultimately his extensive field work, plus additional research by others, conclusively established that many extraordinarily huge and powerful Ice Age floods had shaped the region.
It was in 1923 that Bretz published the first in a series of scientific papers in which he proposed that the severely eroded Channeled Scabland, Dry Falls, and other immense geologic features had been formed by huge, powerful floods that had swept through the Columbia Basin during the Ice Age.
Despite his peers’ doubt and opposition, he resolutely maintained that direct examination of the geologic evidence could lead only to that conclusion. But Bretz was unable to identify the source or cause of such catastrophic flooding.
Earlier, in 1910, another geologist, Joseph T. Pardee, had described evidence of a great ice dammed lake, Glacial Lake Missoula, that had formed during the Ice Age in northwestern Montana. However, Bretz didn’t see the connection between the glacial lake in Montana and the features he described in eastern Washington. Then, in 1940, Pardee reported on his discovery of giant ripple marks, 50 feet high and 200-500 feet apart, that had formed on the floor of Glacial Lake Missoula. These huge, current-related features, along with other newly-found landforms, dramatically confirmed that the lake had suddenly emptied to the west, unleashing the tremendously powerful erosive forces that shaped many of the landforms found in the Columbia Basin. More research followed, and new perspectives became available from aerial photography. Among geologists, the concept of a catastrophic flood came to be accepted by the late 1950s.
Phenomena related to the Ice Age Floods
Recent research has found evidence that comparable floods occurred much earlier in the Ice Age in the Columbia Basin, as much as 1 to 2 million years ago. It has been determined that huge Ice Age glacial-outburst floods occurred in other parts of the world, as well. Even in our own times, similar but much smaller floods have occurred. Scientific study of the Ice Age Floods is contributing to the understanding of cyclical climate change and of very large and destructive contemporary floods on Earth. The Ice Age Floods have also been considered as an analog to understand geologic processes on Mars, where landforms strikingly similar to those in Eastern Washington exist. Could huge floods on this scale happen again? Although global warming may now be a serious concern, it is likely that long-term climate cycles will cause large ice sheets to return at some time in the distant future, and cataclysmic outburst floods will probably recur in this region.
Misconceptions about this Principle
Isn’t it true that human-generated CO2 is just a tiny percent of total CO2 emissions and so cannot be responsible for climate change?
The misconception goes something like this: The oceans contain 37,400 billion tons of suspended carbon, land biomass has 2000-3000 billion tons. The atmosphere contains 720 billion tons and humans contribute only 6 billion tons additional load on this balance. The additional load by humans is incredibly small. A small shift in the balance between oceans and air would cause a much more severe rise in CO2 than anything we could produce.
Atmospheric CO2 is at its highest level in 10 to 15 million years due to the burning of fossil fuels. Human CO2 emissions have upset the natural balance of the carbon cycle.
CO2 in the atmosphere. NASA.
The science says: before the industrial revolution, the CO2 content in the air remained quite steady for thousands of years. Natural CO2 is not static, however. It is generated by natural processes, and absorbed by others. Read More…
Check your Knowledge of this Principle
To pass this knowledge check you will need to have read the main paragraphs for each topic of the principle.