The Intergovernmental Panel on Climate Change released a draft of its Summary for Policy Makers report on Friday 9/28/2013.
This posting is a summary of the main points from that document. The parts in bold font below are direct quotes from that document. I inserted some additional comments clarifying or commenting on those quotes in the text in brackets below each quote.
You can read the entire document by clicking this link - it's about 30pp long:
http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf
Point #1 - Overall state of the climate:
Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.
(In other words, the climate is changing, and not for the better - an observation, not a prediction, not a model)
Point #2 - State of the Atmosphere:
Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850
(Not only is the Earth's surface temperature warmer than it used to be, decade by decade it's getting even warmer - an observation, not a prediction, not a model)
Point #3 - State of the Ocean:
Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010 (high confidence). It is virtually certain (=99-100% confidence) that the upper ocean (0−700 m) warmed from 1971 to 2010
(The upper ocean is warmer than it used to be - an observation, not a prediction, not a model)
Point #4 - State of the Cryosphere (frozen regions):
Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.
(Ice is melting and ice masses are in decling everywhere - an observation, not a prediction, not a model.)
Point #5 - Sea Level:
The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). Over the period 1901–2010, global mean sea level rose by 0.19 [0.17 to 0.21] m
(Sea level has risen 10" - so far - since 1901 - an observation, not a prediction, not a model)
Point #6 - Carbon and other Geochemical Cycles:
The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification.
(Burning fossil fuels together with land use changes produced unprecedented levels of CO2 compared to its levels over the past 800K years - an observation, not a prediction, not a model)
Point #7 - Drivers of Climate Change
Total radiative forcing is positive, and has led to an uptake of energy by the climate system. The largest contribution to total radiative forcing is caused by the increase in the atmospheric concentration of CO2 since 1750.
(Radiative forcing is the term used to determine whether climate is warming or cooling. Positive forcing is warming, negative forcing is cooling. So, the largest contributor to current climate change is CO2 emissions - a conclusion based on many observations.)
Point #8 - Understanding the Climate and its Recent Changes
Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.
(What humans have done and are doing affects climate.)
Point #9 - Evaluation of Climate Models
Climate models have improved since the AR4 (4th assessment report - 2007). Models reproduce observed continental-scale surface temperature patterns and trends over many decades, including the more rapid warming since the mid-20th century and the cooling immediately following large volcanic eruptions (very high confidence)
(Climate models are better than they used to be, and are now quite good at modeling observed climate history and observed current trends in climate change)
Point #10 - 2 Quantification of Climate System Responses:
Observational and model studies of temperature change, climate feedbacks and changes in the Earth’s energy budget together provide confidence in the magnitude of global warming in response to past and future forcing.
(In other words, the accumulated mass of observations collected so far, together with improved climate models increase our confidence that what we think is happening [i.e., human-driven global warming] really is happening.)
Point #11 - Detection and Attribution of Climate Change
Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid 20th century.
(The term "extremely likely" correlates with a statistical significance of 95% confidence, which is about the same degree of scientific confidence we have about the link between tobacco use and cancer. So, the data now show that we are in the realm of scientific certainty that human activities have been the dominant cause of recent observed climate change. Bottom line - HUMANS ARE CAUSING GLOBAL WARMING.)
Point #12 - Future Global and Regional Climate Change
Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.
(Translation - if we just keep doing what we're doing, pumping CO2 into the atmosphere with reckless abandon, things will just keep getting worse. The only way to mitigate the climate change problem is to cut back, way back, on carbon emissions.)
Point #13 - Future of Atmospheric Temperature
Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for all RCP (modeled) scenarios except RCP2.6. It is likely to exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5. Warming will continue beyond 2100 under all RCP scenarios except RCP2.6. Warming will continue to exhibit interannual-to-decadal variability and will not be regionally uniform.
(No matter what we do, the atmosphere is already on a warming trend that will continue for some time to come, even if we cut carbon emissions to zero immediately.)
Point #14 - Future of the Atmosphere: Water Cycle
Changes in the global water cycle in response to the warming over the 21st century will not be uniform. The contrast in precipitation between wet and dry regions and between wet and dry seasons will increase, although there may be regional exceptions.
(Most likely wet areas will get wetter, and dry areas will get drier, with some exceptions. Get ready!)
Point #15 - Future of the Ocean
The global ocean will continue to warm during the 21st century. Heat will penetrate from the surface to the deep ocean and affect ocean circulation.
(The ocean will continue to warm, no matter what we do - this will affect the movement of water, and consequently of heat around the planet)
Point #16 - Future of the Cyrosphere (ice regions)
It is very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow cover will decrease during the 21st century as global mean surface temperature rises. Global glacier volume will further decrease.
(There will be less ice on average, everywhere.)
Point #17 - Future of Sea Level
Global mean sea level will continue to rise during the 21st century. Under all RCP scenarios the rate of sea level rise will very likely exceed that observed during 1971–2010 due to increased ocean warming and increased loss of mass from glaciers and ice sheets.
(No matter what we do, sea level will continue to rise for a prolonged period of time. All we can do now is limit how fast and how high it will rise - this is linked to carbon emissions.)
Point #18 - Carbon and Other Geochemical Cycles
Climate change will affect carbon cycle processes in a way that will exacerbate the increase of CO2 in the atmosphere (high confidence). Further uptake of carbon by the ocean will increase ocean acidification.
(Emitting even more carbon will make things progressively worse, and will drive ocean acidification - a change that will almost certainly affect marine ecosystems and probably cause the extinction of many marine species)
Point #19 - Climate Stabilization, Climate Change Commitment and Irreversibility
Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond. Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped. This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2.
(There is no stopping anthropgenic climate change now, our actions from this point though will determine how far it will go. It's our call.)
Showing posts with label climate. Show all posts
Showing posts with label climate. Show all posts
Sunday, September 29, 2013
Thursday, June 20, 2013
The difference between climate and weather - funny, but true
This posting to "That Videosite.com" attempts to spoof the British Government's commitment to mitigating climate change, but in a strange turn of events actually does a good job of reminding everyone of the difference between climate and weather, and that an unusually cold day doesn't offset the overall long term trend of climate change, a.k.a. global warming. Why not click the link below and give it a look.
Cheers!
http://www.thatvideosite.com/v/2981/global-warming
Cheers!
http://www.thatvideosite.com/v/2981/global-warming
Monday, January 14, 2013
Why has it been so cold in the western USA lately?
The western United States experienced an extremely mild, dry winter during 2011-12. This year (2012-13), however, things are different - it's cold, cold, cold! and wetter than last year, too.
For example, where I live in SE Idaho, we have been experiencing low temperatures in the -10 to -20oF range over the last week or so.
Why is it so much colder than last year?
Last year's mild winter can be explained in part by ongoing global warming, but prevailing weather conditions over the Arctic also matter.
There is something called the Arctic Oscillation (AO). The AO has two phases, a positive and a negative phase. During the Positive Phase of AO, low pressure sits over the Arctic and a high pressure system dominates around 45oN. During the Negative phase of AO, the opposite occurs; a high pressure system dominates the Arctic and low pressure exists around 45oN.
You can learn more about it at this site provided by the National Snow and Ice Data Center (http://nsidc.org/arcticmet/patterns/arctic_oscillation.html)
The bottom line is that the AO can switch between its positive and negative phases over a matter of weeks to decades. The dominating phase of AO can have a significant impacts on the weather over the northern hemisphere.
For example, where I live in SE Idaho, we have been experiencing low temperatures in the -10 to -20oF range over the last week or so.
Why is it so much colder than last year?
Last year's mild winter can be explained in part by ongoing global warming, but prevailing weather conditions over the Arctic also matter.
There is something called the Arctic Oscillation (AO). The AO has two phases, a positive and a negative phase. During the Positive Phase of AO, low pressure sits over the Arctic and a high pressure system dominates around 45oN. During the Negative phase of AO, the opposite occurs; a high pressure system dominates the Arctic and low pressure exists around 45oN.
You can learn more about it at this site provided by the National Snow and Ice Data Center (http://nsidc.org/arcticmet/patterns/arctic_oscillation.html)
The bottom line is that the AO can switch between its positive and negative phases over a matter of weeks to decades. The dominating phase of AO can have a significant impacts on the weather over the northern hemisphere.
(Images courtesy of NSIDC.org)
The image above left shows the effects of the "Positive Phase of Arctic Oscillation". During the positive phase (low pressure system over the Arctic) masses of cold Arctic air stay farther north, and the western USA stays warmer and drier than usual. At the same time, coastal Eastern Canada gets colder air than usual. During the Positive phase the North Atlantic storm track can also move farther north than usual, bringing cold, wet winter weather to northern Europe. According to NSIDC.org, we have been experiencing mainly the positive phase of AO since the 1970s.
The image above right shows the effects of the "Negative Phase of Arctic Oscillation." During the negative phase (high pressure over the Arctic), low pressure is much more common around 45oN, and this phase recently developed. During the negative phase colder, wetter air masses than usual are pulled farther south by the low pressure system over western North America. Along with this we normally see the Atlantic storm track pushed farther south, bringing precipitation to the Mediterranean instead of northern Europe.
There are, of course, many other oscillating weather patterns that contribute to conditions we experience, but the AO is one recently switched phases.
Global Warming also plays an important role in generating weather. Even though the Arctic is cold, much more heat than normal is stored there, and it has to go someplace. One thing this does is increase the amount of atmospheric activity and can contribute energy to the polar jet stream, pushing it farther south than usual. The map below shows the jet stream track for 14 January 2013:
The map above shows the jet stream pushing as far south as northern Mexico. My son happens to be there, and he reported recently that they are experiencing freezing temperatures and even snow!
Knowing something about the Arctic Oscillation effects of global warming help us understand weather we experience.
I hope this was helpful.
Monday, January 7, 2013
2012 - Hot, Hot, Hot! The warmest year on record for Rexburg, Idaho
Every month or so I get a weather summary/update from our local weather guru, Lee Warnick. He enjoys tracking the weather...I enjoy tracking climate.
Anyway, his latest weather news release to the "Rexburg Weather Group" was quite the eye-opener. I mean it shouldn't have been much of a surprise given the un-Idahoanly mild winter we had in 2011-2012, but the effects of global climate change are being felt everywhere, even here in SE Idaho.
Here are some highlights from his weather summary of 2012:
Average annual high temperature data for Rexburg, Idaho (n=41 years of temperature data)
It means that 2012 was the warmest, windiest year on record for Rexburg, Idaho.
Is this an evidence of global warming?
It is statistically difficult to tie an individual weather event, such as one warm year or one windy year, to global warming. But, what we can say with confidence is that the current trend of global climate change makes years like these more likely to occur than in the past, and that the observed elevated temperatures and increased number of windy days are also consistent with climate models of ongoing global warming.
We can also be confident in saying, like it or not, that there will be cooler years than 2012 and warmer years than 2012 in the future, but that we are almost certainly going to see more warmer years than cooler years as long as the current trend of global warming continues.
Anyway, his latest weather news release to the "Rexburg Weather Group" was quite the eye-opener. I mean it shouldn't have been much of a surprise given the un-Idahoanly mild winter we had in 2011-2012, but the effects of global climate change are being felt everywhere, even here in SE Idaho.
Here are some highlights from his weather summary of 2012:
Average annual high temperature data for Rexburg, Idaho (n=41 years of temperature data)
- Average annual high temp = 56.25oF
- 2012 average high temp = 59.36oF
- Departure from average = +3.11oF
- This is the highest annual average temperature on record for Rexburg, Idaho
- Average annual low temperature = 30.59oF
- 2012 annual low temperature = 34.12oF
- Departure from average = +3.53oF
- This was this highest annual low temperature average for Rexburg, Idaho ever
- Average number of 90oF days = 15.6
- 2012 number of 90oF days = 32
- 2012 had more than twice the historical average of 90+oF days!
- Average number of days with below 0oF temperature = 17.5
- 2012 number of days below 0oF = 1...that's right only ONE! Unbelievable!
- Annual average number of windy days = 65.6
- 2012 number of windy days = 104
- Yep, that's 1.6 times more windy days than the historical average.
- The previous record number of windy days/year was 95 in 2011 (also a record at the time)
- High daily temperature records - there were 45 new daily temperature records set in 2012
- Low daily temperature records - there were 6 new daily low temperatures set in 2012.
- If we were in a normal temperature year we would predict roughly equal numbers of high and low temperature records to be set, but in 2012 high temperature records to low temperature records were set at a rate of 7.5:1.
It means that 2012 was the warmest, windiest year on record for Rexburg, Idaho.
Is this an evidence of global warming?
It is statistically difficult to tie an individual weather event, such as one warm year or one windy year, to global warming. But, what we can say with confidence is that the current trend of global climate change makes years like these more likely to occur than in the past, and that the observed elevated temperatures and increased number of windy days are also consistent with climate models of ongoing global warming.
We can also be confident in saying, like it or not, that there will be cooler years than 2012 and warmer years than 2012 in the future, but that we are almost certainly going to see more warmer years than cooler years as long as the current trend of global warming continues.
(image courtesy of allposters.com)
Friday, March 2, 2012
Climate Change 1: Matter, Energy, Weather, and Climate
If you are like me you know at least a few people who have extremely strong opinions about climate change but don't understanding much about climate science. When someone like this enters into a casual conversation about climate change the discussion can quickly turn into an emotionally charged argument. This, in my experience, is both uncomfortable and unproductive.
In order to understand climate change we don't need opinion, we need an understanding of scientific principles and have access to empirical observations. As I hope you read in my earlier posting "On Science 2: Limitations of Science", science can address only questions that are objective and empirical. This means that an objective question has an actual answer that is not based on personal bias or opinion, and that answer can be discovered via empirical evidence.
My goal in sharing these postings on climate change is to provide you with the background and empirical information (observations) you can use to develop your own scientific understanding of this extremely complex and important part of the natural world. I will do my best to emphasize scientific principles and observations and minimize personal bias as I do so.
OK, let's start with some fundamental scientific principles and some definitions that apply to climate (and lots of other things).
Climate is affected by a large variety of factors, but two of the most important ones relate to matter and energy, so let's start there.
The Law of Conservation of Matter:
This law states that matter cannot be created or destroyed, and that changes in matter affect only the form or chemical condition of the matter involved. This means that if matter goes through any kind of change, that you will end up with the same total amount of matter as you started with. For example, If you weigh something before you burn it, and you add the weight of the ash and gases that are released (yeah, gases have mass) you will discover that the total mass before and after the burning is the same. Plus, if you put something in your garbage can and someone picks up your trash and hauls it away, you do not see the trash any more, but it still exists...someplace.
What does this have to do with climate? Climate, as you will see, is all about the movement of matter and the energy it contains around the planet, and the length of time between when energy enters our planet system (atmosphere, ocean, land) and when it leaves. OK, about energy...
The First and Second Laws of Thermodynamics:
I routinely hear people talking about the weather and think that they are talking about climate and vice versa. Since this is the case I think we should take a little time and think about the difference between climate and weather, as well as how they are related to each other.
In doing this I agree with Jack Handey of Saturday Night Live fame who quipped in one of his Deep Thoughts when he said:
So, what do some experts - The National Oceanic and Atmospheric Administration and The National Snow and Ice Data Center - say about these terms?
Weather:
NOAA defines weather this way:
“Weather is the state of atmosphere-ocean-land conditions (hot/cold, wet/dry, calm/stormy, sunny/cloudy) that exist over relatively short periods like hours or days. Weather includes the passing of a thunderstorm, hurricane, or blizzard, a persistent heat wave, a cold snap, a drought. Weather variability and extreme events may respond unpredictably in response to climate change.” (2)
In order to understand climate change we don't need opinion, we need an understanding of scientific principles and have access to empirical observations. As I hope you read in my earlier posting "On Science 2: Limitations of Science", science can address only questions that are objective and empirical. This means that an objective question has an actual answer that is not based on personal bias or opinion, and that answer can be discovered via empirical evidence.
My goal in sharing these postings on climate change is to provide you with the background and empirical information (observations) you can use to develop your own scientific understanding of this extremely complex and important part of the natural world. I will do my best to emphasize scientific principles and observations and minimize personal bias as I do so.
OK, let's start with some fundamental scientific principles and some definitions that apply to climate (and lots of other things).
Climate is affected by a large variety of factors, but two of the most important ones relate to matter and energy, so let's start there.
The Law of Conservation of Matter:
This law states that matter cannot be created or destroyed, and that changes in matter affect only the form or chemical condition of the matter involved. This means that if matter goes through any kind of change, that you will end up with the same total amount of matter as you started with. For example, If you weigh something before you burn it, and you add the weight of the ash and gases that are released (yeah, gases have mass) you will discover that the total mass before and after the burning is the same. Plus, if you put something in your garbage can and someone picks up your trash and hauls it away, you do not see the trash any more, but it still exists...someplace.
What does this have to do with climate? Climate, as you will see, is all about the movement of matter and the energy it contains around the planet, and the length of time between when energy enters our planet system (atmosphere, ocean, land) and when it leaves. OK, about energy...
The First and Second Laws of Thermodynamics:
(FYI - There is ongoing discussion about whether there are three or four laws of thermodynamics, but I will refer to the two laws that are most applicable to questions about climate.)
The first law of thermodynamics: This law is also known as the law of conservation of energy. It states that there is no change in the total amount of energy in a closed system, even if energy within the system changes from one form to another. This law also states that heat will move from a location higher heat/energy to one of lower heat/energy until the closed system reaches thermal equilibrium.
If, however, you observe an open system, such as our planet which has energy coming and going, then energy will either flow into or out of the system depending on the the energy state of the connected systems, e.g., space, the sun, etc.
What does the first law have to do with climate? For one thing, if Earth became a closed system it would eventually reach a state of thermal equilibrium that would be MUCH colder than we experience today. If this happened, there would be no outside energy to drive things like winds, currents, the water cycle of evaporation and precipitation, photosynthesis, and so one. It would be VERY boring to be a weather forecaster or climatologist, because everything would end up being thermally and climatically static.
If, however, you observe an open system, such as our planet which has energy coming and going, then energy will either flow into or out of the system depending on the the energy state of the connected systems, e.g., space, the sun, etc.
What does the first law have to do with climate? For one thing, if Earth became a closed system it would eventually reach a state of thermal equilibrium that would be MUCH colder than we experience today. If this happened, there would be no outside energy to drive things like winds, currents, the water cycle of evaporation and precipitation, photosynthesis, and so one. It would be VERY boring to be a weather forecaster or climatologist, because everything would end up being thermally and climatically static.
The second law of thermodynamics: This law states that when energy is transformed from one form to another the amount of energy available to do work unavoidably decreases, and the balance of energy is called entropy. Entropy is typically released as low-grade heat. For example, an internal combustion energy runs by burning chemical energy in the form of gasoline. The chemical energy in gasoline is converted into mechanical energy that drives the pistons up and down inside the engine. Not all energy that is released when gasoline burns drives the pistons; the balance of energy (entropy) is released as waste heat that you can feel when you touch the engine block.
What does the second law have to do with climate? The energy to run almost all processes on Earth are driven directly or indirectly by sunlight. Sunlight is extremely high quality energy, but when sunlight is absorbed by something, say the seat of your car, that high quality energy is released as low quality heat (I'll discuss this in a later posting in more detail). This means that we need an ongoing supply of high quality energy to keep the planet running. If we didn't have that, entropy would increase until all energy exists only in extremely low-quality forms, and life as we know it could not exist.
What does the second law have to do with climate? The energy to run almost all processes on Earth are driven directly or indirectly by sunlight. Sunlight is extremely high quality energy, but when sunlight is absorbed by something, say the seat of your car, that high quality energy is released as low quality heat (I'll discuss this in a later posting in more detail). This means that we need an ongoing supply of high quality energy to keep the planet running. If we didn't have that, entropy would increase until all energy exists only in extremely low-quality forms, and life as we know it could not exist.
ON TO OTHER THINGS
Before we go farther with this discussion about climate, we should cover a couple of definitions...
Climate and Weather
Before we go farther with this discussion about climate, we should cover a couple of definitions...
Climate and Weather
I routinely hear people talking about the weather and think that they are talking about climate and vice versa. Since this is the case I think we should take a little time and think about the difference between climate and weather, as well as how they are related to each other.
In doing this I agree with Jack Handey of Saturday Night Live fame who quipped in one of his Deep Thoughts when he said:
"Sometimes I think the so-called experts actually are experts."(1)
So, what do some experts - The National Oceanic and Atmospheric Administration and The National Snow and Ice Data Center - say about these terms?
Weather:
NOAA defines weather this way:
“Weather is the state of atmosphere-ocean-land conditions (hot/cold, wet/dry, calm/stormy, sunny/cloudy) that exist over relatively short periods like hours or days. Weather includes the passing of a thunderstorm, hurricane, or blizzard, a persistent heat wave, a cold snap, a drought. Weather variability and extreme events may respond unpredictably in response to climate change.” (2)
The NSIDC defines weather this way:
“Weather is the day-to-day state of the atmosphere, and its short-term (minutes to weeks) variation. Popularly, weather is thought of as the combination of temperature, humidity, precipitation, cloudiness, visibility, and wind.” (3)
Both of these definitions refer to short-term descriptions of atmospheric conditions that are subject to change locally on a minute-to-minute basis.
Climate:
NOAA defines climate this way:
"Climate is the weather pattern we expect over the period of a month, a season, a decade, or a century. More technically, climate is defined as the weather conditions resulting from the mean, or average, state of the atmosphere-ocean-land system, often described in terms of"climate normals" or average weather conditions. Climate Change is a departure from the expected average weather or climate normals." (4)
The NSIDC defines climate this way:
"Climate is defined as statistical weather information that describes the variation of weather at a given place for a specified interval. In popular usage, it represents the synthesis of weather; more formally it is the weather of a locality averaged over some period (usually 30 years) plus statistics of weather extremes. We talk about climate change in terms of years, decades or even centuries. Scientists study climate to look for trends or cycles of variability (such as the changes in wind patterns, ocean surface temperatures and precipitation over the equatorial Pacific that result in El Niño and La Niña), and also to place cycles or other phenomena into the bigger picture of possible longer term or more permanent climate changes." (5)
These definitions refer to a long-term average (usually at least decades long) of the same atmospheric factors we consider when we refer to weather, and can be used to determine whether there is any deviation from long-term averages. These long term shifts or changes are what we refer to as climate change. In addition, some types of climate change can be observed globally, and others can be observed regionally.
Now that we have covered some basic scientific principles and a few definitions, you are ready to move on to the next topic - an introduction to the physical structure and geologic history of the atmosphere, land, and oceans. This information is also an essential component of the foundation of information you will need to understand data about the climate, but this will have to wait until next time - this posting is already too long.
References:
1. Handey, J. 1994. Deepest Thoughts - So Deep They Squeak. Hyperion Press, NY.
“Weather is the day-to-day state of the atmosphere, and its short-term (minutes to weeks) variation. Popularly, weather is thought of as the combination of temperature, humidity, precipitation, cloudiness, visibility, and wind.” (3)
Both of these definitions refer to short-term descriptions of atmospheric conditions that are subject to change locally on a minute-to-minute basis.
Climate:
NOAA defines climate this way:
"Climate is the weather pattern we expect over the period of a month, a season, a decade, or a century. More technically, climate is defined as the weather conditions resulting from the mean, or average, state of the atmosphere-ocean-land system, often described in terms of"climate normals" or average weather conditions. Climate Change is a departure from the expected average weather or climate normals." (4)
The NSIDC defines climate this way:
"Climate is defined as statistical weather information that describes the variation of weather at a given place for a specified interval. In popular usage, it represents the synthesis of weather; more formally it is the weather of a locality averaged over some period (usually 30 years) plus statistics of weather extremes. We talk about climate change in terms of years, decades or even centuries. Scientists study climate to look for trends or cycles of variability (such as the changes in wind patterns, ocean surface temperatures and precipitation over the equatorial Pacific that result in El Niño and La Niña), and also to place cycles or other phenomena into the bigger picture of possible longer term or more permanent climate changes." (5)
These definitions refer to a long-term average (usually at least decades long) of the same atmospheric factors we consider when we refer to weather, and can be used to determine whether there is any deviation from long-term averages. These long term shifts or changes are what we refer to as climate change. In addition, some types of climate change can be observed globally, and others can be observed regionally.
Now that we have covered some basic scientific principles and a few definitions, you are ready to move on to the next topic - an introduction to the physical structure and geologic history of the atmosphere, land, and oceans. This information is also an essential component of the foundation of information you will need to understand data about the climate, but this will have to wait until next time - this posting is already too long.
References:
1. Handey, J. 1994. Deepest Thoughts - So Deep They Squeak. Hyperion Press, NY.
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