Getting Ready for Spring a Few Days Earlier
Getting Ready for Spring
This weekend I plan to work in the garden, start getting dirt ready for spring. Here is the map of the hardiness zones from the U.S. National Arboretum. This map is from 1990, and it is a guide on when to plant based on frost dates.
Figure 1: Planting hardiness zones calculated for 1990 from the U.S. National Arboretum From the documentation of this map. Introduction
This map supersedes U.S. Department of Agriculture Miscellaneous Publication 814, "Plant Hardiness Zone Map," which was revised in 1965. This 1990 version shows in detail the lowest temperatures that can be expected each year in the United States, Canada, and Mexico. These temperatures are referred to as "average annual minimum temperatures" and are based on the lowest temperatures recorded for each of the years 1974 to 1986 in the United States and Canada and 1971 to 1984 in Mexico. The map shows 10 different zones, each of which represents an area of winter hardiness for the plants of agriculture and our natural landscape. It also introduces zone 11 to represent areas that have average annual minimum temperatures above 40 F (4.4 C) and that are therefore essentially frost free.
Last year an updated version of this map was published by the Arbor Day Foundation. This new map got a lot of attention because all the zones moved reflective of persistent warmer weather. That is, planting dates previously appropriate for Kentucky are now appropriate for Indiana and Ohio. There are links on this page that show how the fields have changed (Animation link).
There is a lot of evidence that the Earth is warming. And this warming is persistent enough that it is beginning to change biological activity. Spring is coming earlier and Fall is coming later. One of the papers that I use to introduce the subject is by Gian-Reto Walther and many co-authors, entitled, The Ecological Responses to Recent Climate Change. This paper appeared in Nature in March of 2002. Below is a plot of phenology from this paper. Phenology is the occurrence of natural events, and in this case the phenology is associated with the start of spring.
Figure 2: The start of spring from The Ecological Responses to Recent Climate Change
This figure is from observations taken in Germany. Along the horizontal axis are years, and on the vertical axis on the left is the number of days earlier (-) or later (+) that a certain event has occurred. On the right vertical axis is a measure of temperature and the North Atlantic Oscillation Index. The different lines are Temperature (March, April, May), Temperature (March and April); spring arrival of birds and hatching in flycatchers, and the unfurling of leaves in two types of trees (Betula Pendula (a birch) and Aesculus hippocastanum (horse chestnut)) . The yellow line on the figure is the North Atlantic Oscillation (NAO) index, which is a measure of atmospheric variability. (Here is a link to NAO data.)
Spring is coming earlier. Over this set of observations spring is 2-3 days earlier in 2000 that it was in 1950. One thing to point out in the graph is that since 1985 the curves have moved steadily towards the earlier onset of spring. (Note this is the same time of the observations that were used in the update of the hardiness zones by the Arbor Day Foundation (above)).
Of interest to the weather people amongst us is the link to the North Atlantic Oscillation. (Here is a blog for last year on the NAO.) The NAO is a natural model of variability that impacts the temperature in Europe. These natural modes raise the level of “noise” when trying to determine if there is a long-term temperature trend. To make it more difficult, these natural modes, which have a cyclic character, are not independent of carbon dioxide related global warming. They will likely change.
r
|
Updated: 5. maaliskuuta 2009 klo 03:27 (GMT)
|
Permalink |
A A A
|
Models(5): Where do requirements come from?
Requirements vs Requirements of scientists
I sit in my share of meetings on models and modeling. I listen to plans about model development and impassioned statements of the importance of “the science.” There are struggles on how to make the interface to other communities, the proverbial policymaker. In a room full of scientists they always come around to the need to follow “the science.”
What does it mean to follow “the science?” Science is a process of investigation – a method. It is one of several ways that we generate and accumulate knowledge.
Following the science always generates a number of research projects, which usually fall on two paths. There is the path of inclusion - adding additional processes to models, for example, adding land-ice parameterizations, making the carbon-cycle interactive or improving the radiative treatment of aerosols. There is a path of higher resolution and increased rigor and accuracy in a component model like the atmosphere; for example, moving to algorithms that represent the non-hydrostatic processes in the atmosphere and resolve the behavior of cloud systems. This is the path of increased fidelity to the first principles of physics – or chemistry, or biology. There is always tension between increased fidelity and more inclusion. The tension is related to both limited computational and intellectual resources.
The motivations that drive the advocacy for these different paths are well grounded. In general, a group of priorities rise to the top, and they address, demonstrably, important problems. The importance is determined, often, by uncertainty. For example, the uncertainty associated with the model’s ability or inability to represent clouds. Since increased clouds provide a cooling term, determination of changes to clouds are important to knowing how fast the planet will warm.
Scientists identify the uncertainties and the source of the uncertainties. They develop strategies to address these uncertainties. The determination of priorities to address these uncertainties is an imperfect process, and the “requirements” appear as a list of important problems. Outside of the science community, the value of addressing these uncertainties might be unclear.
The publication of the 2007 IPCC report fundamentally changes the demand for climate information by society. This challenges the traditional approach of developing requirements for model development based on the uncertainties of climate predictions. The result of this challenge will be two paths of scientific investigation: a traditional path of basic research that is focused on addressing the greatest uncertainties in climate predictions, and a second path that develops science-based climate information based on requirements that come from a wide variety of applications. This second path is applied research.
To some extent, both paths currently exist, but the exploding demand for climate information will amplify the applied research path. For a given application, for example the impact of the development of a large corn-based ethanol energy capability, it is possible to analyze the impact on water resources and carbon balances. An analysis can be made from existing data bases of observations and simulation experiments. But this is a process that relies largely on using information that was developed to perform basic research of the climate system. The details of the application extend the information in these data bases beyond the purposes for which the information was developed. Spatial and temporal resolution are, perhaps, too coarse; the impact of urban environments and water engineering not adequately considered. It would be possible to design numerical experiments with existing models and computational resources that would provide science-based investigation with, potentially, much more robust information for the application at hand.
The process of developing models to address the uncertainties in the climate system, the requirements of scientists, are often of little relevance to addressing the applications that are important for adaptation to climate change. Improvement of the representation of marine stratus clouds, a priority in improving our understanding of the climate system, will not be consequential to the water resource manager in the western United States. ( blog on role of uncertainty )
The time scale for the development of policy is, now, a small number of years. The life time for energy infrastructure is a small number of decades, and decisions on the nature of expenditures in energy infrastructure are needed today. The development and implementation of strategies to manage water in an environment where less water is stored in ice and snow are already under consideration. ( California water and climate change ) The design and funding of adaptation plans for societal infrastructure near sea level is imperative. ( Impacts of Climate Variability and Change on Transportation Systems and Infrastructure -- Gulf Coast Study ) The information needed for these decisions will be demanded on time scales that are much shorter than the development cycles of climate models that are pursuing traditional scientific development paths.
It is imperative that the climate science community develop the capabilities to provide the best science-based answers to these externally posed applications at any given time. A natural response to this demand for information is the development of a climate service, perhaps in the spirit of the National Weather Service. In the U.S. this approach to providing environmental information has often led to the dichotomy of research versus operations. In this dichotomy the flow from research to operations is inefficient. We need a more modern approach.
This is a blog, not an essay ... stopping here - looking for reactions.
r
Figure 1: From the European Sea Level Service , a focused collaborative organization.
|
Updated: 8. marraskuuta 2009 klo 21:50 (GMT)
|
Permalink |
A A A
|
Models(4) Iconic Figure:
Models(4) Iconic Figure:
Of the figures that I consider the Iconic Figures of climate, there is one based totally on models. A recent version of this figure from the IPCC 2007 is given here.
Figure 1: Observations and simulation of the past century from the IPCC 2007 Technical Summary (Working Group 1) (largish PDF).
This is a figure of, approximately, the last century. In this figure there are three traces. One of traces, the black one, is of the observed, globally averaged surface temperature record. In the bottom figure is a blue curve, which is a model simulation that does not include anthropogenic (human-related) forcing. That is, it is “natural” forcing. In the top curve there is a red curve that is a model simulation that includes both natural and anthropogenic forcing. The point of this figure is that both natural and anthropogenic forcing is important, and that the recent warming requires the inclusion of anthropogenic forcing to simulate the recent observed temperature increase.
Forcing: For the purpose of this figure, “forcing” are those things that change the ability of the Earth to absorb or reflect radiative energy. Another “forcing” is the radiative energy that comes from the Sun. “Natural” forcing starts with the variability of the Sun. Of special importance in the realm of natural forcing is the impact of volcanic eruptions. Large volcanic eruptions put aerosols into the atmosphere. Aerosols above the Earth’s surface can reflect more solar radiation or they can absorb radiation in the atmosphere. These help cool the surface of the Earth. Aerosols also impact the infrared radiation; that is, the radiation emitted by the Earth back to space. Other natural forcings include water in the atmosphere, in all phases, and carbon dioxide. In general, these model experiments assume that the amount of carbon dioxide in the atmosphere prior to, about, 1850 is “natural.” Of course, the amount of solar radiation that is reflected by the surface is also included – ice and land.
In contrast to “natural” forcing is anthropogenic or human-related forcing. This is change in the forcing relative to the natural forcing. The most important of the anthropogenic forcings is due to carbon dioxide, which is calculated as the additional forcing due to the increased amount of carbon dioxide relative to the “pre-industrial” amount of carbon dioxide. Pre-industrial forcing is linked to about the year 1850. There are other greenhouse gases like methane, nitrous oxide, and the chlorofluorocarbons. Nitrous oxide increases are largely related to use of synthetic fertilizers. Other anthropogenic changes in the radiative balance of the Earth are related to changes in reflection at the surface due to how we use land.
The Plot: Here is my description of this plot. The dark red and the dark blue lines are averages from many model simulations. The light lines that surround the dark lines are all of the individual simulations. Prior to 1950 the natural and anthropogenic simulations are not much different from each other. After 1960 only the plot with anthropogenic forcing follows the temperature observations. Perhaps more importantly, the natural and anthropogenic curves diverge from each other as time goes along.
The light lines surrounding the dark lines give some idea of model variability. It is notable that, for the most part, this variability covers the range of variability in the observations. The models do not follow, point by point, the shorter scale variability in the observations, for example between 1920 and 1930. The models have variability, such as the El Nino – La Nina and North Atlantic Oscillation. The spread of the models suggests that the model variability covers this range of variability, but the models are not tracing this variability on an event-by-event basis. The comparable spread in the models and the observations also serve as a sanity check that the models represent variability in the same range as the Earth’s climate.
The simulations do show the impact of several large volcanic eruptions. The volcanoes do cause cooling of the globe. Volcanic eruptions, and especially the well observed Mount Pinatubo eruption in 1991, provide opportunities to evaluate processes in models.
It is also of interest to examine where the models and the observations do not agree. A most interesting period is from 1935-1940, a period when the planet was warm. (Thanks to crucilandia for pointing a reference to get me started.) A substantial literature is developing that examines this period. It seems to be associated with substantial Arctic warming. It is a period that demands more study. The cooling that all of the models calculate about 1915 is also interesting.
An important take away message from these simulations is that there are factors other than carbon dioxide that cause temperature variability. Hence, carbon dioxide and temperature are not necessarily correlated on shorter scales of variability. (This is a like my wave metaphor on this blog. )
Conclusions: This is a figure open to interpretation. Personally, I find this figure compelling. I know how difficult it has been to develop the models and to specify the forcing. There is also a huge depth of analysis at different levels of detail and averaging that support the conclusion that it is only with increasing carbon dioxide forcing that the recent temperature increase can be explained.
Others can look at this plot, and come to a different conclusion. One issue that many raise is what about the treatment of aerosols? This is a process in models which has substantial uncertainty in its quantification.
Looking forward to the comments.
Here are the previous blogs on models.
Uncertainty and Types of Models
Models (1) Assumptions
Models (2) Forgotten Layers
Models (3) Predictable Arguments
|
Updated: 8. marraskuuta 2009 klo 21:50 (GMT)
|
Permalink |
A A A
|
Water, Water, Water (2): Water Vapor Feedback
Water, Water, Water(2): Water Vapor Feedback
This follows from the previous water blog, links below.
Water is a greenhouse gas. In fact, in the Earth’s radiative balance, water is the most important greenhouse gas. Its influence on the radiative budget is larger than the influence of carbon dioxide. Water is, however, different from carbon dioxide in several important ways. First, water exists in all of its phases in the normal range of temperatures observed on Earth. When the phase changes, energy is consumed or released. As water vapor is carried around in the atmosphere and its phase changes, energy is transported. When water turns to ice, its normal path in clouds, and then into water, it falls out of the atmosphere. Hence, the second major difference compared with carbon dioxide, it cycles quickly. Any particular water molecule spends a much shorter time in the atmosphere than a molecule of carbon dioxide.
There is also the ocean. From the point of view of the atmosphere, the ocean is a nearly infinite supply of water vapor. The atmosphere is constantly replenished with water after in falls out. Since the air can hold more water if it gets warmer, one consequence of warming at the Earth’s surface is more water in the atmosphere. If water gets deposited as snow and ice on the surface, then it can stay there for a while. (This is the big difference when compared with Mars, on Mars a large portion of the atmosphere is deposited in the polar caps. Very different balance!)
This blog will focus on water in the atmosphere.
Because of this fast cycling of water with this large reservoir, we don’t think of water in the same way as we think of carbon dioxide. The atmosphere, more or less, holds the amount of water it can hold at any given the temperature. Yes, we emit water from industry and in cooling towers. But it immediately becomes integrated into the water cycle; it does not accumulate like carbon dioxide.
The cycling of water is closely related to vertical motion in the atmosphere. When warm wet surface air rises, the air cools. This will not change with climate change, warm air will rise and it will cool and water will condense and it will rain --- and snow. Again, in clouds water vapor is normally converted to ice and then turns into water or snow as it falls through the warmer air below.
When water vapor turns into ice or liquid, its role in the radiative balance of the Earth changes. As ice or liquid, water is a cloud and then becomes a reflector of solar radiation; hence, it has a cooling effect. Water in the atmosphere – it’s a greenhouse gas, it contributes to energy transport, it’s a reflective particle.
Imagine that the climate of the Earth is a balance of some type. Then when we add a long lived greenhouse gas like carbon dioxide to the atmosphere, then it is reasonable to ask the question how will the balance change? To first approximation the surface will warm from the additional carbon dioxide. Then, the atmosphere and ocean will respond. The responses in the atmosphere and ocean might amplify the warming by carbon dioxide; they might reduce the warming by carbon dioxide; they might do nothing. Because we are in this temperature range where water changes phases so readily, water is at the center of this response. The response to a change in a balance is called a feedback. A positive feedback amplifies the change, and a negative feedback reduces the change. The feedback called the water vapor feedback is one of the most important and most easily analyzed atmospheric responses. It is a positive feedback. Basically as the atmosphere warms it holds more water, which acts as a greenhouse gas, and warms the atmosphere some more.
Figure 1: Water Vapor Feedback in a Warming Atmosphere
If you wanted to think about this in the same way as carbon dioxide, as something we are adding to the atmosphere, then adding carbon dioxide leads to us adding water as well. This is due to temperature increases. In an earlier blog I mentioned a paper that I thought was especially important. It was a paper about what is changing in the radiative balance of the Arctic sea ice, and what was measured was an increase in surface warming due to an increase in water vapor due to an increase in air temperature. Here’s that reference again. (Sea Ice Arctic
There is a lot of chatter about all of the ice and snow we have seen this winter. In the U.S. you might also think of it as ice and snow followed by fog because of rapid melting. (Yes, there is fog at the Chicago airport today.) In an earlier blog, I talked about the fact that increased water vapor would likely build up the Greenland and East Antarctic ice sheets because they are at high elevation. It’s cold up there; it stills snows; there is more water to snow. This is true in the Sierra Nevada as well. It can still snow a lot, but it is likely to melt a lot as well.
Let’s think about cold a little more. In the winter, at the pole, it is dark. It still gets cold at the pole. With climate change, it will still get dark at the pole, and it will be cold. It might not be as cold, as long, but it is still cold. (Have you read To Build a Fire? – “It was cold.”) And the atmosphere still has to get cold air away from the pole and warm air to the pole. That is the job of the atmosphere. When that cold air gets wrapped up with warm wet air, it still freezes and it still snows. That the globe gets warm on average does not mean it will not snow. It might not even mean in a cumulative way, it will snow less. What are the other attributes of snow, and snow cover, and melting, and fog, and water storage that might be a better measure of whether or not there is warming?
r
Previous Blogs on Water and Feedbacks
Water Water Water (1)
Warm Snow
Clouds Cool and Warm
Cooling Aerosols
|
Updated: 8. marraskuuta 2009 klo 21:51 (GMT)
|
Permalink |
A A A
|
