Great question and one we jump right into in our kick-off post to distinguish important words – starting with weather and climate.
When it comes to “climate” and “weather,” we often use the same words to describe them. Lovely. Harsh. Delightful. Brutal.
So is it any wonder why there is confusion between the two? Indeed, the need for word distinction between this pairing is so apparent, many scientific agencies make it a point to explain their meanings on their websites.
In a nutshell, weather is what we’re seeing right now.
Climate is the long-term – usually 30 years – of weather averages. It’s not shocking that it’s sunny and nice out in San Diego in July. It’d be shocking if a downpour were happening right now. Historically, it rarely rains in San Diego in July. The only umbrellas you see are the big ones on the beach for shade and the little ones in cocktails for garnish.
But these words are key today. Can we have a discussion about climate and record-breaking weather if we don’t share the same definition of these words? Sure. But would it be productive? Probably not. Knowing the distinction is important given that we need to survive – and ideally thrive – in both the immediate timeframe and the longer term horizon.
It’s the hottest summer on record. Is that weather a result of a changing climate or is it happenstance?
Our two guest bloggers this week on this word distinction are experts addressing questions like that. Christina Milesi, PhD is a research scientist working in the Ecological Forecasting Lab at NASA Ames Research Center in Moffett Field in Silicon Valley. She’s also a member of the NASA Climate Change Adaptation Science Investigator Group for NASA Ames. We met her last year when she was making a presentation in the San Francisco Bay Area. The focus of her presentation – the difference between climate and weather. We’re thrilled to have her comment here on our blog. Next, we’ll hear from Cara Pike, the Director of Climate Access, which serves as the bridge between climate research and government agencies and organizations that are trying to spur action. We look forward to posting both their interviews next week.
Most of us associate NASA with the space shuttle and landing people on the moon, not with weather or climate. What’s NASA’s role in studying these?
You are right; most people are unaware that one of NASA’s goals is to “Expand scientific understanding of the Earth.” One of NASA’s missions is to explore the Earth system from space through observations taken mainly from satellites. These satellites, designed and launched by NASA itself, orbit our planet measuring various aspects of our Earth system, from sea surface temperature to snow cover, and over long period of times they allow us to improve our understanding of how climate on our planet is changing, and the impacts of these changes on the biosphere. A list of data collected by NASA’s Earth Science missions can be found visiting the following website: http://gcmd.nasa.gov/.
In your words, what is the difference between climate and weather?
Weather is the day-to-day variation. We call those meteorological variables or temperature, precipitation, humidity, wind. Climate is the average of the weather recorded in a location over a long period of time in addition to its statistical variability. For example, the summer climate of San Diego, where your business is, is the statistical average of the meteorological conditions of June, July and August recorded around San Diego for about 30 years. So on average we expect the summer in San Diego to be warm and sunny because of its climate, but there can be colder and cloudy days even in July if a low-pressure system lingers along the coast. This unexpected variability is caused by the weather.
Are you studying climate or weather and how do you study it?
I study the impact of climate on the biosphere. I use Earth observations from satellites to measure the effect of climate and its changes on the greenness of the landscapes. This tells us how changes in temperature, precipitation and atmospheric CO2 affect the photosynthetic capacity of the biosphere, and its ability to sequester carbon. I also use vegetation models, which are mathematical representations of the photosynthetic activity of biomes and the associated fluxes in carbon, nitrogen, and water to understand how vegetation growth could change in the next 50 to 100 years in response to projected climate change, and how this could potentially affect the functioning of ecosystems.
We’re a communications firm and our colleagues and clients are trying to engage and inform the public and policy makers about important topics, like climate change. What do you think the most effective ways are to communicate about climate and the difference between climate and weather?
I find that some of these abstract concepts can be explained by making analogies with everyday activities, for example driving to work. Let’s suppose that your commute to work by car on average takes half our, but at least 40 minutes if there is a lot of traffic, and up to 1 hour if there’s an accident. However, if you commute off rush hours it will take you only 20 minutes. You can think of the average commute as the climate, and all its day-to-day variations caused by traffic, accidents, road constructions, as the weather. In this analogy, you can imagine a changing climate caused by more and more cars put on the road. These increase your average commute, and make the delays caused by extra traffic and accidents even more extreme. Robert Heinlein famously defined the difference between weather and climate by saying that “Climate is what you expect, weather is what you get.”
Our firm is based in San Diego. Here we have what’s described as a Mediterranean climate. How many climate types are out there?
Well, let’s think about what impacts the climate of a location.
Climate is first of all determined by the latitude of a location, because the latitude regulates how the sun strikes the earth surface, which affects the temperature of the location. In the tropics the sun strikes directly over the head, so it heats the surface more. As the latitude increases, the angle at which the sunrays hit the earth generally increases, and so does the distance from the sun.
In addition to the latitude, the climate of a location is also impacted by its altitude — which affects mainly the air pressure and the temperature, the terrain — which affects the wind circulation, and the distance to water bodies, which also impacts the wind circulation and affects the amount of moisture in the air and the precipitation. One way to classify climates is according to the Köppen climate classification system, which divides the world based on the combinations of temperature and precipitation and their distribution throughout the year. The Köppen system groups regions with similar average temperature and precipitation regimes, and defines about two dozens different climatic regimes, of which the Mediterranean climate is one of them.
And I take it certain weather patterns exist in these climates. Is that why people confuse the two words?
That’s right, there are prevailing weather patterns in any given climate and their average over long time defines the climate. In San Diego there are mostly sunny and dry days in the summer and mild and rainy winters, which determines San Diego to be located in a Mediterranean climatic regime. People have often a short-term memory regarding meteorological conditions, and often attribute any wild weather condition to climate. To understand climate you need to maintain a big picture and rely on accurately measured long records in meteorological variables.
Thank you for being interviewed. We value your input greatly and are excited to share your thoughts with our colleagues and readers. We ask all interviewees whether they have any recommendations for resources (books conferences, organizations, etc) or experts that you’d like to recommend be highlighted in future posts. Please feel free to add any referrals you have here:
I would like to recommend the book: The Weather of the Future, by Heidi Cullen.
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Thank you Dr. Milesi for your time and thoughts. We appreciate it greatly. In the coming days, we will run Part II of word distinction between “weather” and “climate” when we hear from Cara Pike, the Director of Climate Access.
Mike Stetz, Senior Writer
Collaborative Services, Inc.