Category Archives: sustainability

Sustainable Landscaping

Added references Updated again below, `Plants of the future’, 2018-05-03 Update, 2018-04-29: While my first thoughts and reasons for this post were simply to collect together a number of links pertaining to an interesting subject, regarding which there appeared to … Continue reading

Posted in adaptation, American Association for the Advancement of Science, argoecology, biology, Botany, Carl Safina, complex systems, conservation, ecological services, Ecological Society of America, ecology, Ecology Action, environment, fragmentation of ecosystems, invasive species, land use to fight, living shorelines, New England, population biology, population dynamics, quantitative biology, quantitative ecology, sustainability, sustainable landscaping, water as a resource | 1 Comment

(reblog) Bill Ritter, Jr, Colorado State University: “Market forces are driving a clean energy revolution in the U.S.”

Transforming U.S. energy systems away from coal and toward clean renewable energy was once a vision touted mainly by environmentalists. Now it is shared by market purists. Today, renewable energy resources like wind and solar power are so affordable that … Continue reading

Posted in American Solar Energy Society, Amory Lovins, Bloomberg New Energy Finance, BNEF, bridge to somewhere, Buckminster Fuller, clean disruption, CleanTechnica, decentralized electric power generation, decentralized energy, destructive economic development, economics, EIA, electricity, electricity markets, investment in wind and solar energy, Joseph Schumpeter, Michael Osborne, solar democracy, solar domination, solar energy, solar power, sustainability, the energy of the people, the green century, Tony Seba, wind energy, wind power, zero carbon | Leave a comment

“Eon and RWE just killed the utility as we know it”

The story’s at Bloomberg.

Posted in Bloomberg, Bloomberg New Energy Finance, bridge to somewhere, Buckminster Fuller, business, CleanTechnica, decentralized electric power generation, decentralized energy, demand-side solutions, economics, EIA, electricity, electricity markets, energy utilities, grid defection, investing, investment in wind and solar energy, investments, Joseph Schumpeter, local generation, local self reliance, marginal energy sources, microgrids, nonlinear systems, regulatory capture, risk, Sankey diagram, solar democracy, solar domination, solar power, stranded assets, supply chains, sustainability, the energy of the people, the green century, the value of financial assets, tragedy of the horizon, unreason, utility company death spiral, wind energy, wind power | Leave a comment

“Carbon emissions and climate: Where do we stand, and what can be done if it all goes wrong?”

On Sunday, 11th February 2018, I presented an Abstract of a 3 hour talk on the subject, “Carbon emissions and climate: Where do we stand, and what can be done if it all goes wrong?” at the Needham Lyceum, hosted … Continue reading

Posted in Anthropocene, being carbon dioxide, Carbon Cycle, carbon dioxide, carbon dioxide capture, carbon dioxide sequestration, Carbon Tax, civilization, clear air capture of carbon dioxide, climate, climate change, climate disruption, COP21, Cult of Carbon, differential equations, dynamical systems, ecology, emissions, environment, exponential growth, fossil fuel divestment, fossil fuel infrastructure, fossil fuels, geoengineering, geophysics, Glen Peters, Global Carbon Project, global warming, greenhouse gases, Humans have a lot to answer for, Hyper Anthropocene, investments, James Hansen, Kerry Emanuel, liberal climate deniers, Mark Carney, Michael Bloomberg, Minsky moment, mitigation, nonlinear, nonlinear systems, oceanography, phytoplankton, population biology, population dynamics, precipitation, Principles of Planetary Climate, quantitative biology, quantitative ecology, radiative forcing, rationality, Ray Pierrehumbert, risk, sea level rise, sociology, stranded assets, supply chains, sustainability, T'kun Olam, the right to be and act stupid, the right to know, the tragedy of our present civilization, the value of financial assets, thermohaline circulation, tragedy of the horizon, unreason, UU, UU Needham, Wally Broecker, zero carbon | Leave a comment

on nonlinear dynamics of hordes of people

I spent a bit of last week at a symposium honoring the work of Charney and Lorenz in fluid dynamics. I am no serious student of fluid dynamics. I have a friend, Klaus, an engineer, who is, and makes a … Continue reading

Posted in Anthropocene, bifurcations, biology, Carl Safina, causation, complex systems, dynamic generalized linear models, dynamic linear models, dynamical systems, ecological services, ecology, Emily Shuckburgh, finance, Floris Takens, fluid dynamics, fluid eddies, games of chance, Hyper Anthropocene, investments, Lenny Smith, Lorenz, nonlinear, numerical algorithms, numerical analysis, politics, population biology, population dynamics, prediction markets, Principles of Planetary Climate, public transport, Ray Pierrehumbert, risk, sampling networks, sustainability, Timothy Lenton, Yale University Statistics Department, zero carbon, ``The tide is risin'/And so are we'' | 1 Comment

wind+storage 2.1 ¢/kWh, solar+storage 3.6 ¢/kWh

Update, 2018-01-16 Vox has a widely acclaimed update to this story. (rubbing hands gleefully) Utility scale bids at Xcel Energy had median prices of 2.1 ¢/kWh for wind-with-storage, and 3.6 ¢/kWh for solar-with-storage. Hat tip to Utility Dive. In U.S. … Continue reading

Posted in American Petroleum Institute, American Solar Energy Society, Amory Lovins, Bloomberg New Energy Finance, BNEF, bridge to somewhere, Buckminster Fuller, Cape Wind, Carbon Worshipers, clean disruption, CleanTechnica, climate economics, corporate litigation on damage from fossil fuel emissions, Cult of Carbon, decentralized electric power generation, decentralized energy, destructive economic development, distributed generation, economics, electrical energy storage, electricity, electricity markets, energy storage, energy utilities, FERC, Green Tech Media, ILSR, investment in wind and solar energy, Joseph Schumpeter, leaving fossil fuels in the ground, local generation, local self reliance, marginal energy sources, Massachusetts Clean Energy Center, microgrids, natural gas, petroleum, pipelines, public utility commissions, PUCs, rate of return regulation, regulatory capture, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, stranded assets, sustainability, the energy of the people, the green century, the value of financial assets, Tony Seba, tragedy of the horizon, wind energy, wind power, zero carbon | Leave a comment

FERC: No multi-billion dollar bailout for coal and nuclear generating facilities

Excerpts from statements by Richard Glick, FERC commissioner are given below. The Microgrid Knowledge (“MGK”) news article summarizes the context by writing: The commission rejected the energy secretary’s assertion that retirement of coal and nuclear plants threatens electric resilience. Instead … Continue reading

Posted in American Association for the Advancement of Science, American Solar Energy Society, Amory Lovins, Berkeley, Bloomberg New Energy Finance, BNEF, CleanTechnica, climate economics, decentralized electric power generation, distributed generation, electricity markets, energy utilities, FERC, green tech, grid defection, ILSR, investment in wind and solar energy, ISO-NE, John Farrell, Joseph Schumpeter, microgrids, rate of return regulation, stranded assets, sustainability, the energy of the people, the value of financial assets, Tony Seba, wind energy, wind power | Leave a comment

Michael Bloomberg speaks on the Sustainability Accounting Standards Board

Posted in Amory Lovins, Anthropocene, Bloomberg, Bloomberg New Energy Finance, BNEF, Michael Bloomberg, Michael Osborne, planning, resiliency, Richard Branson, stranded assets, supply chains, sustainability, Tony Seba | Tagged | Leave a comment

Disaster planning in a new climate, inland from the coasts

See Glynis Board’s “The New Normal: Super Storms Highlight Importance Of Disaster Planning”.

Posted in adaptation, American Meteorological Association, American Statistical Association, AMETSOC, Anthropocene, bridge to nowhere, climate disruption, flooding, floods, games of chance, hurricanes, hydrology, meteorology, National Center for Atmospheric Research, NCAR, New England, nor'easters, precipitation, resiliency, risk, statistics, sustainability, the tragedy of our present civilization, the value of financial assets, tragedy of the horizon | Leave a comment

`Insurance companies should collect a carbon levy`

From Anthony J Webster and Richard H Clarke in Nature, “Insurance companies should collect a carbon levy”: Governments juggle too many interests to drive global action on climate change. But the insurance industry is ideally placed. With annual premiums amounting … Continue reading

Posted in American Statistical Association, Anthropocene, attribution, Bloomberg New Energy Finance, bridge to somewhere, business, capitalism, Carbon Tax, climate business, climate economics, corporate litigation on damage from fossil fuel emissions, corporations, Cult of Carbon, economics, energy levy, finance, fossil fuel divestment, fossil fuels, global warming, Hyper Anthropocene, insurance, investments, Joseph Schumpeter, leaving fossil fuels in the ground, moral leadership, statistics, stranded assets, sustainability, the right to know, the value of financial assets, tragedy of the horizon, transparency, zero carbon | Leave a comment

On the responsibilities of scientists

On 4 September 2017, I added a blog post here titled “On the responsibilities of engineers”. Scientists have responsibilities, too. And I am delighted to say that the National Academies have just demonstrated a proud example of how such responsibilities … Continue reading

Posted in American Association for the Advancement of Science, American Statistical Association, anti-science, attribution, Boston Ethical Society, chemistry, citizenship, compassion, Donald Trump, dump Trump, ecology, Ecology Action, economics, environment, environmental law, Environmental Protection Agency, ethics, evidence, fossil fuels, justice, land use to fight, leaving fossil fuels in the ground, pollution, rationality, reason, reasonableness, risk, science, science denier, secularism, sustainability, the right to be and act stupid, the right to know, the stack of lies, the value of financial assets, tragedy of the horizon | Leave a comment

Amory Lovins, 2008: `Natural Capitalism: The Next Industrial Revolution with Amory Lovins`

An excellent presentation from über successful dropout from Harvard University and Oxford University, Dr Amory Lovins, at University of California at Berkeley:

Posted in Adam Smith, affordable mass goods, American Association for the Advancement of Science, Amory Lovins, Anthropocene, Bloomberg New Energy Finance, bridge to somewhere, capitalism, climate economics, destructive economic development, ecological services, ecology, Ecology Action, economic trade, economics, environment, ILSR, internal inconsistency, Joseph Schumpeter, leaving fossil fuels in the ground, population biology, population dynamics, quantitative biology, resource producitivity, solid waste management, stranded assets, supply chains, sustainability, the green century, the right to know, the tragedy of our present civilization, the value of financial assets, transparency | Leave a comment

The South Shore Recycling Cooperative can save you money!

Abington, Cohasset, Duxbury, Hanover, Hanson, Hingham, Hull, Kingston, Middleboro, Norwell, Plymouth, Rockland, Scituate, Weymouth, Whitman Join ’em. Ask your town governors on the South Shore to check ’em out. It’s your tax dollars wasted if you don’t. What your town … Continue reading

Posted in Amory Lovins, Anthropocene, argoecology, coastal communities, composting, destructive economic development, ecological services, ecology, economics, environment, environmental law, Equiterre, Hyper Anthropocene, John Farrell, leaving fossil fuels in the ground, local self reliance, oceanography, Our Children's Trust, pollution, recycling, Sankey diagram, sociology, South Shore Recycling Cooperative, stranded assets, sustainability, the green century, UU Needham | Leave a comment

Schroders asset management forecasts global warming of more than +4℃

(Updated Thursday, 27 July 2017) Schroders is a global asset management firm. They very recently issued a warning that current global trends put the planet on track for more than +4℃ warming. The full news brief, from them, is available … Continue reading

Posted in adaptation, Anthropocene, Buckminster Fuller, climate business, climate disruption, climate economics, corporate litigation on damage from fossil fuel emissions, corporate supply chains, disingenuity, dynamical systems, economics, environmental law, forecasting, fossil fuel divestment, fossil fuel infrastructure, global blinding, global warming, Hyper Anthropocene, investing, investments, leaving fossil fuels in the ground, Schroders, sea level rise, Spaceship Earth, sustainability, temporal myopia, the right to be and act stupid, the show, the tragedy of our present civilization, the value of financial assets, tragedy of the horizon, zero carbon | 1 Comment

The Myth of Baseload Power (Amory Lovins)

Posted in Amory Lovins, Anthropocene, Bloomberg New Energy Finance, BNEF, Buckminster Fuller, capitalism, decentralized electric power generation, decentralized energy, design science, distributed generation, economics, energy efficiency, energy reduction, environment, Hermann Scheer, Hyper Anthropocene, ILSR, integrative design, John Farrell, Joseph Schumpeter, leaving fossil fuels in the ground, local generation, local self reliance, microgrids, petroleum, reasonableness, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, sustainability, the energy of the people, the green century, the right to know, utility company death spiral, wind energy, wind power, zero carbon | 1 Comment

Solar Costs at `Jaw-Dropping Lows`; `No Evidence That Changing Power Mix Endangers Electric System Reliability`

From GTM: `Solar Moves in a Curious Direction Since Trump Quit Paris Deal: Up‘ There is “[n]o evidence that the changing power mix endangers electric system reliability”. Two reports: Advancing past baseload to a flexible grid Electricity Markets, Reliability and … Continue reading

Posted in American Solar Energy Society, Anthropocene, Bloomberg, Bloomberg New Energy Finance, BNEF, bridge to somewhere, Buckminster Fuller, clean disruption, climate business, corporate litigation on damage from fossil fuel emissions, decentralized electric power generation, decentralized energy, demand-side solutions, destructive economic development, distributed generation, Donald Trump, economics, electricity markets, engineering, force multiplier, fossil fuel divestment, fossil fuel infrastructure, Green Tech Media, grid defection, Hyper Anthropocene, ILSR, investment in wind and solar energy, Joseph Schumpeter, leaving fossil fuels in the ground, local generation, local self reliance, microgrids, public utility commissions, reasonableness, Sankey diagram, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, stranded assets, sustainability, the energy of the people, the green century, the right to be and act stupid, the value of financial assets, Tony Seba, tragedy of the horizon, utility company death spiral, wind energy, wind power, zero carbon | 5 Comments

Statements by the Ecological Society of America on the proposed U.S. exit from the Paris Agreement, and on Climate Change

By withdrawing from the Paris Agreement on climate change, the United States is abdicating its role as the world leader in using science-based information to inform policy. Business, political, and scientific leaders the world over are condemning the decision. More … Continue reading

Posted in adaptation, American Association for the Advancement of Science, American Statistical Association, Anthropocene, argoecology, Carl Safina, climate change, climate disruption, complex systems, ecological services, ecology, Ecology Action, environment, global warming, Hyper Anthropocene, marine biology, mesh models, model-free forecasting, population biology, population dynamics, quantitative biology, quantitative ecology, science, Science magazine, Spaceship Earth, sustainability, Takens embedding theorem, the tragedy of our present civilization, the value of financial assets, tragedy of the horizon, Wordpress, zero carbon | Leave a comment

Installed Non-Utility Solar, Massachusetts, 12/2016

(Click on image to see a larger figure, and use browser Back Button to return to blog.)

Posted in Bloomberg New Energy Finance, BNEF, clean disruption, CleanTechnica, decentralized electric power generation, decentralized energy, destructive economic development, distributed generation, electricity markets, energy utilities, engineering, feed-in tariff, green tech, grid defection, ILSR, investment in wind and solar energy, ISO-NE, John Farrell, local generation, local self reliance, making money, Massachusetts Clean Energy Center, microgrids, New England, regime shifts, RevoluSun, solar democracy, solar domination, solar energy, solar power, stranded assets, SunPower, sustainability, the energy of the people, the green century, the value of financial assets, utility company death spiral, zero carbon | Leave a comment

GForce Waste Sorters!

Waste management at the Boston Red Sox. Check out their Wide World of Waste.

Posted in ecology, Ecology Action, economics, materials science, recycling, resiliency, solid waste management, sustainability | Leave a comment

`Exxon Shareholders Approve Climate Resolution: 62% Vote for Disclosure’

Flash from InsideClimate News: ExxonMobil shareholders voted Wednesday to require the world’s largest oil and gas company to report on the impacts of climate change to its business—defying management, and marking a milestone in a 28-year effort by activist investors. … Continue reading

Posted in Anthropocene, Bloomberg, Bloomberg New Energy Finance, BNEF, bridge to nowhere, business, capitalism, Carbon Worshipers, clean disruption, climate, climate business, climate change, climate disruption, climate economics, corporations, destructive economic development, environmental law, extended supply chains, Exxon, fossil fuel divestment, fossil fuel infrastructure, fossil fuels, Global Carbon Project, global warming, greenhouse gases, Hyper Anthropocene, investing, investments, Joseph Schumpeter, leaving fossil fuels in the ground, making money, Our Children's Trust, petroleum, pollution, rationality, reason, reasonableness, statistics, stranded assets, sustainability, the right to know, the tragedy of our present civilization, the value of financial assets, tragedy of the horizon, zero carbon | Leave a comment

“The [transport-as-a-service] disruption will crater the value chain of the oil industry” (RethinkX)

… By 2030, the report predicts that oil demand will drop to 70 million barrels per day. The resulting collapse in prices will be catastrophic for the industry, and these effects are likely to be felt as early as 2021. … Continue reading

Posted in American Petroleum Institute, Bloomberg New Energy Finance, BNEF, bridge to somewhere, Buckminster Fuller, capitalism, clean disruption, CleanTechnica, climate business, decentralized energy, destructive economic development, economics, efficiency, fossil fuel divestment, green tech, ILSR, investments, John Farrell, leaving fossil fuels in the ground, local self reliance, making money, Mark Jacobson, Massachusetts Clean Energy Center, public transport, public utility commissions, rationality, reason, stranded assets, sustainability, the energy of the people, the green century, the value of financial assets, Tony Seba, zero carbon | Leave a comment

Why we sold our Disney Vacation Club timeshares

Hat tip to Climate Denial Crock of the Week, in their “Florida slowly confronting sea level nightmare.”

Posted in Anthropocene, being carbon dioxide, Bloomberg, carbon dioxide, climate, climate change, climate disruption, climate economics, coastal communities, coasts, Disney, Disney Vacation Club, environmental law, flooding, Florida, global warming, greenhouse gases, Hyper Anthropocene, Joe Romm, leaving fossil fuels in the ground, living shorelines, science education, shorelines, sustainability, the right to be and act stupid, the tragedy of our present civilization, the value of financial assets | Leave a comment

“You don’t have that option.”

Dr Neil deGrasse Tyson. I think he’s awesome. Marvelous. I saw him in Boston. He and I did not get off well, at the start, because of my being awestruck, and feeling very awkward, and the short time we had … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, American Statistical Association, AMETSOC, Bayesian, citizen data, citizen science, Climate Lab Book, Earth Day, ecological services, ecology, environment, Hyper Anthropocene, Neill deGrasse Tyson, Principles of Planetary Climate, rationality, Ray Pierrehumbert, reason, reasonableness, religion, science, science education, Science magazine, scientific publishing, secularism, Spaceship Earth, sustainability, the right to be and act stupid, the right to know, the tragedy of our present civilization, United States, XKCD | Leave a comment

Net energy consumption at Westwood Studios, after solar generation, with zero Carbon house, and, now, Chevy Volt

I don’t have time to offer much in the way of explanation or comments here, but here’s the status of consumption per day, in Kilowatt-hours. Update: I should have provided some context. (Click on image to see a larger figure, … Continue reading

Posted in adaptation, American Solar Energy Society, Anthropocene, Bloomberg New Energy Finance, BNEF, bridge to somewhere, Buckminster Fuller, clean disruption, CleanTechnica, decentralized electric power generation, decentralized energy, demand-side solutions, distributed generation, efficiency, electricity, electricity markets, energy utilities, green tech, Hermann Scheer, Hyper Anthropocene, investment in wind and solar energy, ISO-NE, local generation, local self reliance, microgrids, Sankey diagram, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, sustainability, the energy of the people, the green century, the value of financial assets, Tony Seba, zero carbon | 1 Comment

`Environmental science in a post-truth world’ (Lubchenco and Kammen)

Jane Lubchenco is a Professor at Oregon State University, and was administrator of the U.S. NOAA from 2009 through 2013, the U.S. Science Envoy for the Ocean at the State Department from 2014 to 2016, and the president of the … Continue reading

Posted in Akaike Information Criterion, American Association for the Advancement of Science, American Statistical Association, being carbon dioxide, Buckminster Fuller, climate, climate change, coastal communities, coasts, ecological services, ecology, environment, environmental law, evidence, global warming, Humans have a lot to answer for, Hyper Anthropocene, ignorance, Jane Lubchenco, marine biology, mass extinctions, population biology, population dynamics, quantitative biology, quantitative ecology, risk, science, Spaceship Earth, sustainability, T'kun Olam, temporal myopia, the tragedy of our present civilization | Leave a comment

SunPower

Posted in Anthropocene, Bloomberg New Energy Finance, CleanTechnica, decentralized electric power generation, decentralized energy, green tech, Hyper Anthropocene, Joseph Schumpeter, Mark Jacobson, Sankey diagram, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, sustainability, the energy of the people, the green century, Tony Seba, zero carbon | Leave a comment

`Moving forward on climate change and sustainability`

From WGBH, and hat tip to Environmental Justice TV, includes Dr Gavin Schmidt speaking, who I was especially interested in, and whose talk begins here: Interesting that Dr Schmidt has some gentle criticism of the PBS program NOVA. Whole talk … Continue reading

Posted in American Association for the Advancement of Science, American Meteorological Association, AMETSOC, Anthropocene, bridge to nowhere, Buckminster Fuller, carbon dioxide, climate, climate change, climate data, climate disruption, Ecology Action, environment, Equiterre, fossil fuel divestment, Gavin Schmidt, geophysics, greenhouse gases, Hyper Anthropocene, investment in wind and solar energy, Kevin Anderson, moral leadership, NASA, physics, science, Spaceship Earth, sustainability, the tragedy of our present civilization, the value of financial assets, zero carbon | Leave a comment

Our daily electricity consumption since May 2016

(To see a larger figure, click on image, and use browser Back Button to return to blog.)

Posted in Bloomberg New Energy Finance, BNEF, decentralized electric power generation, decentralized energy, demand-side solutions, distributed generation, efficiency, electricity, electricity markets, energy reduction, energy utilities, engineering, evidence, fossil fuel divestment, green tech, grid defection, Hermann Scheer, investment in wind and solar energy, John Farrell, Joseph Schumpeter, Kevin Anderson, leaving fossil fuels in the ground, local generation, local self reliance, Mark Jacobson, Massachusetts Clean Energy Center, microgrids, RevoluSun, Sankey diagram, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, stranded assets, sustainability, the energy of the people, the green century, the value of financial assets, Tony Seba, utility company death spiral, zero carbon | Leave a comment

Climate Potpourri: Flooding and Solar (both from Ars)

And they who will not be ready, will suffer the economic consequences. Ready for flooding: Boston analyzes how to tackle climate change (That water is a foot deep, previously reported in a post here. Click on image to see larger … Continue reading

Posted in adaptation, American Meteorological Association, American Solar Energy Society, AMETSOC, Anthropocene, Bloomberg New Energy Finance, Boston, carbon dioxide, citizenship, civilization, CleanTechnica, climate, climate business, climate change, climate disruption, climate economics, coastal communities, environment, flooding, floods, fossil fuels, global warming, green tech, greenhouse gases, Hyper Anthropocene, ice sheet dynamics, investment in wind and solar energy, John Englander, Joseph Schumpeter, leaving fossil fuels in the ground, living shorelines, Massachusetts, Massachusetts Clean Energy Center, meteorology, oceanography, resiliency, shorelines, solar democracy, solar domination, solar energy, solar power, Spaceship Earth, sustainability, T'kun Olam, the energy of the people, the green century, the value of financial assets | Leave a comment

Sleeping Giant Awakening

Originally posted on Climate Denial Crock of the Week:
https://twitter.com/johnmyers/status/809097380456865792 Wikipedia: Isoroku Yamamoto’s sleeping giant quotation is a quote by the Japanese Admiral Isoroku Yamamoto regarding the 1941 attack on Pearl Harbor by forces of Imperial Japan. The quotation is portrayed at the very end of…

Posted in adaptation, American Association for the Advancement of Science, American Meteorological Association, American Solar Energy Society, American Statistical Association, AMETSOC, Anthropocene, California, Carbon Worshipers, citizen data, citizen science, climate, climate change, climate data, climate disruption, data science, Donald Trump, ecology, Ecology Action, geophysics, global warming, Hyper Anthropocene, ignorance, Jerry Brown, science, sustainability, the right to be and act stupid, the right to know, the stack of lies, the tragedy of our present civilization | Leave a comment