From the bottom of the ocean to the surface of the Sun, instruments on weather stations, buoys, satellites, and other platforms collect climate data. To learn about past climates, scientists use natural records, such as tree rings, ice cores, and sedimentary layers. Historical observations, such as native knowledge and personal journals, also document past climate change. Jump to “Environmental observations are the foundation for understanding the climate system”
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What You Need to Know About Principle 6: Understanding Climate
Our understanding of the climate system is improved through observations, theoretical studies, and modeling. When it comes to climate, how do scientists know what they know? While studies indicate that climate researchers virtually all agree that human activities are altering the climate system, the general public is under the impression that scientists are still debating whether or not humans are through their activities changing climate. You might wonder why this is. Here’s a clue: politics and money—neither of which are science— have played a big role in shaping public beliefs. This principle concerns key elements of climate studies and the "self-correcting" peer review process. Click the tabs below to learn more:
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We Can Understand and Predict the Behavior of the Climate System
The Earth’s climate system is subject to the same physical laws as the rest of the Universe. Therefore, the behavior of the Earth’s climate can be understood and predicted through careful, systematic study.
But it is not uncommon for the topic of climate change to be intermixed with politics in general discussions and sometimes the politics overtake the science. Read more…
watch the video and compare the work scientists do to understand the climate with that of politicians and pundits
Environmental Observations are the Foundation for Understanding Climate and How it is Changing
From the bottom of the ocean to the surface of the Sun, instruments on weather stations, buoys, satellites, and other platforms collect climate data. To learn about past climates, scientists use natural records, such as tree rings, ice cores, and sedimentary layers. Historical observations, such as Native American knowledge and personal journals, also document past climate change. View some of these scientists at work.
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Muir Inlet, Glacier Bay National Park and Preserve, Alaska
Repeat Photography of Glaciers
One type of environmental observation to detect how the climate is changing is to study glaciers. Most glaciers have been relatively stable for thousands of years but are now shrinking and disappearing. The U.S. Geological Survey uses repeat photography to detect these changes, comparing photos taken in the past (mid to early in the last century) with those taken in recent years (during this century). You can use the sliders on the photos below to see how (from left to right) the Eliot Glacier on Mount Hood and the Emmons Glacier on Mount Rainier have changed over time.
Observations and experiments are used to construct and refine climate models
The models represent our climate system and they make predictions about its future behavior. Results from these models lead to better understanding of the links between the atmosphere-ocean system and the climate and inspire more observations and experiments. Over time, this process of running the model, making more observations, and conducting experiments, then refining the model and running it again results in more and more reliable projections of future climate conditions.
Given how complex the climate system is and how difficult it is to predict weather, how can computer models possibly simulate the future climate? This question is frequently raised in the public debates around climate change, but much less frequently among scientists familiar with the contributions modeling has made to climate science. Read more…
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Our understanding of climate differs in important ways from our understanding of weather
Our understanding of climate differs in important ways from our understanding of weather. Climate scientists’ ability to predict climate patterns months, years, or decades into the future is constrained by different limitations than those faced by meteorologists in forecasting weather days to weeks into the future.
Weather forecasters try to answer questions like: What will the temperature be tomorrow? Will it rain? How much rain will we have? Will there be thunderstorms? Today, most weather forecasts are based on models. A weather forecaster looks at the model output to figure out the most likely scenario. The accuracy of weather forecasts depend on both the model and on the forecaster's skill. Weather forecasts are accurate for up to a week.
Climate predictions take a much longer-term view. These predictions try to answer questions like how much warmer will the Earth be 50 to 100 years from now? Read More…
How Foresters in the Pacific Northwest Use Climate Models to Predict Changes in Ecosystems
In trying to predict future climate changes, it is vital to carefully choose the right models to use and to be careful in how you use them.
“The problem is that models have to simplify the world,” says Dave Peterson, a research forester with the PNW Research Station. “But they can be useful for giving us ideas about what we should be looking for and where we should be looking for it.”
Models that look at potential impacts on a particular resource, such as snowmelt, hydrology, or vegetation, can provide valuable perspectives, but Peterson warns land managers to proceed with caution.
“A species distribution model might say that a plant species is likely to move 100 miles north in the future,” he says. “But the model can’t tell you how it would get there, or how well it will compete with the vegetation that’s already there.”
Although longer-term growing conditions might be suitable for a particular species in a new location, the path to that location may not be straightforward. For example, higher temperatures and less precipitation could make it difficult for seeds to regenerate, or a disturbance might make it difficult for seeds to land in suitable habitat.
“You could be looking at a two- or three- hundred-year window—it has a pretty good chance of happening, but it could be a pretty messy couple of centuries,” says Peterson.
The study team looked at a wide range of vegetation models. It reviewed the major classes of vegetation models; described their basic function, strengths, and weak- nesses; discussed the contribution each could make toward understanding and projecting vegetation responses to future climatic changes; and made recommendations about how to use the output.
“Model output can be used as a basis for discussion among resource teams that are considering management and climate change adaptation actions,” says Kerns, “but we suggest that folks also factor in long-term data from the paleoecological record (data from fossils to reconstruct the ecosystems of the past.), observational and experimental studies, and local knowledge, to assess potential and plausible climate-change effects. We want people to step away from thinking about models as a definite forecast, and instead use them as a ‘what if’ scenario—more of a thought process than a prediction.”
The research team synthesized multiple model projections for future vegetation responses to disturbances, changing environmental controls, and elevated atmospheric carbon dioxide for key species in the five major biomes of the Pacific Northwest. The models agree that alpine and subalpine forests and habitats are most at risk, primarily because of warming temperatures, earlier snowmelt, and longer growing seasons.
Models for dry coniferous forests, savannas and woodlands, and shrub-steppe are less consistent in their predictions. “The models generally predict warmer temperatures, but they tend to be a little inconsistent about precipitation,” says Peterson. “It’s harder to make confident decisions based on the projections from these models for some of those biomes.”
Misconceptions about this Principle
Scientists can’t even predict the weather, how can they predict the climate?
The misconception or myth goes something like this: “..Since modern computer models cannot, with any certainty, predict the weather two weeks from now, how can we rely upon computer models to predict what the Earth's climate might be like a hundred years from now? They can't! Yet people want you to believe that these models can predict the future. I bet I can do at least as well with a crystal ball.”
Climate models do not predict day to day weather, which can be variable. Instead, they predict climate averages.
The science says: this claim is based more on an appeal to emotion than fact. The inference is that climate predictions, decades into the future, cannot be possibly right when the weather forecast for the next day has some uncertainty. In spite of the claim in this myth, short term weather forecasts are highly accurate and have improved dramatically over the last three decades. Read more…