Environmental Awereness

How well have climate models projected global warming?

Scientists have been making projections of future global warming using climate models of increasing complexity for the past four decades.

Climate models, driven by atmospheric physics and biogeochemistry, play an important role in our understanding of the Earth’s climate and how it will likely change in the future.

Carbon Brief has collected prominent climate model projections since 1973 to see how well they project both past and future global temperatures.

While some models projected less warming than we’ve experienced and some projected more, all showed surface temperature increases between 1970 and 2016 that were not too far off from what actually occurred, particularly when differences in assumed future emissions are taken into account.

How have past climate models fared?

While climate model projections of the past benefit from knowledge of atmospheric greenhouse gas concentrations, volcanic eruptions and other radiative forcingsaffecting the Earth’s climate, casting forward into the future is understandably more uncertain. Climate models can be evaluated both on their ability to hindcast past temperatures and forecast future ones.

Hindcasts – testing models against past temperatures – are useful because they can control for radiative forcings. Forecasts are useful because models cannot be implicitly tuned to be similar to observations. Climate models are not fit to historical temperatures, but modellers do have some knowledge of observations that can inform their choice of model parameterisations, such as cloud physics and aerosol effects.

In the examples below, climate model projections published between 1973 and 2013 are compared with observed temperatures from five different organizations. The models used in the projections vary in complexity, from simple energy balance models to fully-coupled Earth System Models.

(Note, these model/observation comparisons use a baseline period of 1970-1990 to align observations and models during the early years of the analysis, which shows how temperatures have evolved over time more clearly.)

Sawyer, 1973

One of the first projections of future warming came from John Sawyer at the UK’s Met Office in 1973. In a paper published in Nature in 1973, he hypothesised that the world would warm 0.6° C between 1969 and 2000, and that atmospheric CO2 would increase by 25%. Sawyer argued for a climate sensitivity – how much long-term warming will occur per doubling of atmospheric CO2 levels – of 2.4° C, which is not too far off the best estimate of 3° C used by the Intergovernmental Panel on Climate Change (IPCC) today.

Unlike the other projections examined in this article, Sawyer did not provide an estimated warming for each year, just an expected 2000 value. His warming estimate of 0.6° C was nearly spot on – the observed warming over that period was between 0.51° C and 0.56° C. He overestimated the year 2000’s atmospheric CO2 concentrations, however, assuming that they would be 375-400 ppm – compared to the actual value of 370 ppm.

Broecker, 1975

The first available projection of future temperatures due to global warming appeared in an article in Science in 1975 published by Columbia University scientist Prof. Wally Broecker. Broecker used a simple energy balance model to estimate what would happen to the Earth’s temperature if atmospheric CO2 continued to increase rapidly after 1975. Broecker’s projected warming was reasonably close to observations for a few decades, but recently has been considerably higher.

This is mostly due to Broecker overestimating how CO2 emissions and atmospheric concentrations would increase after his article was published. He was fairly accurate up to 2000, predicting 373 ppm of CO2 – compared to actual Mauna Loa observations of 370 ppm. In 2016, however, he estimated that CO2 would be 424 ppm, whereas only 404 ppm has been observed.

Broecker also did not take other greenhouse gases into account in his model. However, as the warming impact from methanenitrous oxide, and halocarbons has been largely cancelled out by the overall cooling influence of aerosols since 1970, this does not make that large a difference (though estimates of aerosol forcings have large uncertainties).

As with Sawyer, Broecker used an equilibrium climate sensitivity of 2.4° C per doubling of CO2. Broecker assumed that the Earth instantly warms up to match atmospheric CO2, while modern models account for the lag between how quickly the atmosphere and oceans warm up. (The slower heat uptake by the oceans is often referred to as the “thermal inertia” of the climate system.)


Cont. reading...



A Research Report by Beth Carruthers 

It might seem at first blush that artists and scientists approach the world in very different ways. In popular culture, the former might be stereotyped as frivolous and disconnected from the “real world”, and the latter as unimaginative and concerned only with “hard facts”. Like most stereotypes, these are doomed to inaccuracy. In reality, the two have much in common, and where they do not, they can be most complimentary. Environmental philosopher Allen Carlson for instance, claims that one can have aesthetic appreciation of the environing world only through science, ie, through understanding how things work together beautifully in natural systems.


Beth Carruthers 2006

Artists and scientists alike begin their working projects and processes with a question – an enquiry. They are located within and asking questions of the same world. Processes and final manifestations of the work can differ greatly, yet goals may be parallel. Increasingly, when it comes to ecology and the environmental sciences many artists, scientists and environmental groups are asking similar questions and looking for solutions to the same, increasingly global, problems.

Similar questions about how we may improve human/world relations might involve finding and designing solutions to polluted waters, recovering and preserving habitats and species, educating people about the mystery of the other than human world and how everyday lifestyle choices impact this habitat we share.

Increasingly, the sciences and environmental groups are looking to the arts for partnership, collaboration and translation of vital information into forms that reach individuals, communities and organizations. The arts can facilitate a process of learning through the engaged senses, bypassing conditioned patterns of thinking and allowing other ways of knowing to come forward, at times subtly, at times overwhelmingly. Whether the work focuses on natural, cultural, or political aspects of their environing world, artists have always been sensitive and responsive to the world. The role of artist as catalyst, critic, and educator is hardly a new development. Oftentimes the work has been urgent, prodded into becoming by the nature of a crisis, catastrophe or political repression.

Never, though, has the role of the arts been so urgent as it is in the face of what is now obvious to all as an immediate global crisis within our sustaining and environing world. Because this crisis has been and continues to be nurtured and produced by past and current cultural practices and ideologies, artists, immersed in world and cultural practices, are ideally situated to locate and develop responses.

But if environmental groups and scientists increasingly look to artists for collaboration, many contemporary artists are just as frequently turning to scientists and ecologists for their detailed analysis of our interdependent world. As collaborators in artistic projects, ecologists and scientists provide in-depth research about, and a sophisticated understanding of, the interconnectedness of natural systems that can prove inspirational and efficacious in the design and implementation of EcoART works. 

Cont. reading...

A Declaration of Concern (Old & New)

On June 1 and 2, 1966, at Independence Hall in Philadelphia, a small group of landscape architects who shared a concern for the quality of the American environment and its future were assembled by the Landscape Architecture Foundation. This was their declaration:

We urge a new, collaborative effort to improve the American environment and to train a new generation of Americans equipped by education, inspiring example and improved organizations to help create that environment.

A sense of crisis has brought us together. What is merely offensive or disturbing today threatens life itself tomorrow. We are concerned over misuse of the environment and development which has lost all contact with the basic processes of nature. Lake Erie is becoming septic, New York City is short of water, the Delaware River is infused with salt, the Potomac River with sewage and silt. Air is polluted in major cities and their citizens breathe and see with difficulty. Most urban Americans are being separated from visual and physical contact with nature in any form. All too soon life in such polluted environments will be the national human experience.

There is no “single solution” but groups of solutions carefully related one to another. There is no one-shot cure, nor single-purpose panacea, but the need for collaborative solutions. A key to solving the environmental crisis comes from the field of landscape architecture, a profession dealing with the interdependence of environmental processes.

Man is not free of nature’s demands, but becomes more dependent upon nature. Natural resources are where they are — not where we wish them to be. Those who plan for the future must understand natural resources and processes. These are the basis of life and the prerequisite for planning the good life. They must know geology, physiography, climatology, ecology to know why the world’s physical features are where they are; and why plants, animals and man flourish in some places and not in others. Once they understand landscape capabilities — the “where” and “why” of environment, the determinants of change — they can then interpret the landscape correctly. Only then are they qualified to plan and design the environment.

Like the architect, the landscape architect practices an historic art. However, the landscape architect is uniquely rooted in the natural sciences. He is essential in maintaining the vital connection between man and nature.

The demand for better resource planning and design is expanding… Today’s demands require far more landscape architects than are available. Schools are expanding, as are the ranks of practitioners, but they are stretched thin. The gap between demand and supply widens. The environment is being built hastily and too often without such professional advice or help. In the process, far too much is damaged beyond recall.

The solution of the environmental crisis demands the skills of many professions. So that the landscape architects may make their vital contribution, we propose a four-point program to bridge the gap between knowledge and practice: (1) recruitment, (2) education, (3) research and (4) a nationwide system for communicating the results of research, example and good practice. Its purpose is to multiply the effectiveness of the limited number of landscape architects, while producing more trained people to cope with the future environment.

We pledge our services. We seek help from those who share our concern.

Campbell Miller
Grady Clay
Ian L. McHarg
Charles R. Hammond
George E. Patton
John O. Simonds

On June 10-11, 2016, over 700 landscape architects with a shared concern for the future were assembled by the Landscape Architecture Foundation (LAF) at the University of Pennsylvania in Philadelphia. Inspired by LAF’s 1966  Declaration of Concern, we crafted a new vision for landscape architecture for the 21st century. This is our call to action.

Across borders and beyond walls, from city centers to the last wilderness, humanity’s common ground is the landscape itself. Food, water, oxygen – everything that sustains us comes from and returns to the landscape. What we do to our landscapes we ultimately do to ourselves. The profession charged with designing this common ground is landscape architecture.

After centuries of mistakenly believing we could exploit nature without consequence, we have now entered an age of extreme climate change marked by rising seas, resource depletion, desertification and unprecedented rates of species extinction. Set against the global phenomena of accelerating consumption, urbanization and inequity, these influences disproportionately affect the poor and will impact everyone, everywhere.

Simultaneously, there is profound hope for the future. As we begin to understand the true complexity and holistic nature of the earth system and as we begin to appreciate humanity’s role as integral to its stability and productivity, we can build a new identity for society as a constructive part of nature.

The urgent challenge before us is to redesign our communities in the context of their bioregional landscapes enabling them to adapt to climate change and mitigate its root causes. As designers versed in both environmental and cultural systems, landscape architects are uniquely positioned to bring related professions together into new alliances to address complex social and ecological problems. Landscape architects bring different and often competing interests together so as to give artistic physical form and integrated function to the ideals of equity, sustainability, resiliency and democracy.

As landscape architects we vow to create places that serve the higher purpose of social and ecological justice for all peoples and all species. We vow to create places that nourish our deepest needs for communion with the natural world and with one another. We vow to serve the health and well-being of all communities.

To fulfill these promises, we will work to strengthen and diversify our global capacity as a profession. We will work to cultivate a bold culture of inclusive leadership, advocacy and activism in our ranks. We will work to raise awareness of landscape architecture’s vital contribution. We will work to support research and champion new practices that result in design innovation and policy transformation.

We pledge our services. We seek commitment and action from those who share our concern.