Long-abolished discriminatory lending practices in the US are still having an impact on the inequality of climate risks facing urban populations today, according to a new study.
The research, published in Nature Cities, looks at historically “redlined” neighbourhoods – those deemed highly risky for lenders, broadly due to the race and economic profile of those in the area – and compares them to neighbourhoods that were seen as less risky.
The scientists find that, across more than 200 US cities, once-redlined neighbourhoods are at higher risk of heat exposure and flooding.
Even homes just tens of metres apart have different climate risks, they find, with those located on the redlined side of a boundary at higher risk than those living on the other side of the boundary.
The lead author of the study tells Carbon Brief that the work underscores the historical legacy of planning decisions made in the last century, adding that she hopes that current policymakers can better consider the “impact of different planning policies and the unintended consequences”.
One researcher who was not involved in the study tells Carbon Brief that the work makes several significant contributions, but cautions that the authors were “pretty bold” in some of their conclusions.
‘Risky’ investments
“Redlining” refers to a discriminatory historical practice in the US, whereby neighbourhoods were graded as too “risky” for investment based on race, income levels and housing quality. These grades were used as justification for the denial of long-term mortgages and exacerbated existing racial segregation.
One of the most recognisable remnants of redlining is the set of maps produced by the Home Owners’ Loan Corporation (HOLC), established in 1933 as part of US president Franklin D Roosevelt’s “New Deal”. The HOLC refinanced foreclosed mortgages at lower interest rates with the intention of preserving and expanding homeownership.
The HOLC created maps of “riskiness” of investment in an attempt to guarantee that the loans would be paid back and that the burden on the taxpayer would be minimal.
The maps created by the HOLC classified neighbourhoods based on a four-point risk scale, with A-grades – the “best”, or least-risky, investments – outlined in green and D-grades – the most risky, termed “hazardous” – outlined in red, giving rise to the term.
B-graded neighbourhoods, outlined in blue, were termed “still desirable”, while C-graded ones, in yellow, were “declining”.
The HOLC created maps for more than 200 cities across at least 40 states. Other federal agencies and private companies later made their own “risk-assessment” maps, further cementing the practice into policy.
Although redlining was formally outlawed in 1968 by the US Fair Housing Act, the inequalities created and exacerbated by the practice persist in many places to this day, says Dr Arianna Salazar-Miranda, an urban planner and data scientist at Yale University.
Salazar-Miranda, who is the lead author of the new study, tells Carbon Brief:
“There are many social and economic dimensions for which we should be worried about this long-standing legacy of redlining.”
For example, previous research has shown that redlined neighbourhoods have lower rates of homeownership, lower credit scores and lower home values. There are also associations between historically redlined neighbourhoods and prevalence of cancer and asthma, air pollution and proximity to hazardous waste, among other dimensions of health inequality and environmental racism.
Prof Shannon Van Zandt, an urban planner at Texas A&M University, who was a reviewer of the new paper, but not involved in the study itself, tells Carbon Brief:
“Segregation is still so relevant in the experiences of families of colour and, in particular, Black or African American households, because of the very indelible lines that we literally drew [on the map].”
Climate risk
Using maps from 202 cities across the US, Salazar-Miranda and her colleagues examine the risk of heat extremes and flooding for homes in differently graded neighbourhoods. These factors, each graded on a 1-10 scale from least to most hazardous, were developed by the climate research and technology firm First Street.
The heat risk factor combines temperature and humidity to determine a “feels-like” temperature, averaged across the month of July for each location.
The flood risk factor uses flooding factors, such as rainfall and high tide levels, as well as variables that affect water runoff, including elevation and ground permeability. It also incorporates existing community flood defences. The risk is defined by both depth and likelihood of flooding.
Both the heat and flood risk scores also factor in projections of future climate change, including higher temperatures and sea level rise.
The researchers focused specifically on homes within 100 metres of a boundary between two different grades. Salazar-Miranda tells Carbon Brief:
“We’re trying to narrow down on a subset of properties that are very comparable, where they have the same underlying conditions and the only thing that changed is whether they’re on one side of the border or the other.”
The maps below show the digitised redlining map of Baltimore (left), with the colours indicating the different grades and the bold lines depicting boundaries between different grades.
On the right, a zoomed-in portion of the map shows the 100-metre buffer zones drawn around each boundary. Locations of houses are coloured according to which side of the border they fall on – grey for the lower-graded side and black for the higher-graded side.
Geographical and climatic features, such as elevation and amount of rainfall, did not vary significantly across the boundaries because the researchers were only looking at homes close to a grade boundary.
They find that, aggregated across all cities, D-graded neighbourhoods have a flood risk factor that is 0.245 points higher than A-graded ones – more than three times higher than the additional risk of a C-graded neighbourhood.
The heat risk effect is smaller, but still significant, with D-graded neighbourhoods scoring 0.033 points higher than A-graded neighbourhoods.
The chart below shows the flood and heat exposure risks for neighbourhoods graded B, C and D, relative to the average risk for A-graded neighbourhoods. While both risk factors increase as the grade decreases, the effect is much more pronounced for flood risk.
They also find that flood risk factor increases by 0.1 points, or about 5.5% on average, for homes that are on the lower-graded side of a border, as compared to homes on the higher-graded sides. For the heat risk factor, this figure is 0.011 points.
Although the absolute change in the heat risk factor is relatively small, Salazar-Miranda tells Carbon Brief that these “very small changes…can really harm your health”. She adds:
“It really depends on your pre-determinants of health – how healthy you are, how well you eat, whether you have diabetes or an underlying health condition. And we know that these are particularly worse in disadvantaged communities.”
Doing the analysis on a parcel-scale – namely, house-by-house – is one of the most significant contributions of the new work, says Prof Vivek Shandas, a professor of geography focusing on urban climate at Portland State University in Oregon, who was not involved in the new research. However, Shandas adds:
“There’s a lot that happens across 200 or 100 metres in a city…If we’re doing parcel-scale assessments, we need to get parcel-scale understanding of movement of water and the way that heat is distributed.”
‘Environmental capital’
The researchers then investigate a potential mechanism for how historical redlining could still be impacting vulnerability to current and future climate risks.
They propose that lower-graded neighbourhoods had less investment in what they call “environmental capital”, such as trees, public parks and drainage systems.
This, they say, could be due to a combination of factors: lower property values in the neighbourhoods reduces the communities’ tax income that could be invested in such projects; places with high levels of income inequality tend to have lower community engagement; and low homeownership rates can lead to reduced community investment in public goods, such as parks.
As a proxy for environmental capital investment, the authors look at four measurable factors of environmental quality: tree canopy, street-level vegetation, ground-surface perviousness and home foundation height. Tree cover and street-level vegetation can both mitigate heat risk by providing shade and inducing a cooling effect. More pervious ground surfaces allow more drainage, while higher foundations can decrease an individual home’s risk of flooding.
They find that for each measure of environmental quality, lower-graded neighbourhoods score progressively worse than higher-graded ones, as seen in the chart below.
Houses in D-graded neighbourhoods are, on average, nearly 5.7 percentage points less pervious and have 3.4 percentage points less tree cover than those in A-graded areas.
Similarly, homes on the lower-graded side of a border have lower perviousness and foundations closer to the ground level than homes on the higher-graded side, by 1.9 and 2 percentage points, respectively. Tree canopy and street-level vegetation differ between the two by 1.03 and 1.2 percentage points.
Shandas tells Carbon Brief that introducing the idea of capital into this type of analysis is “really interesting”, but the claims the authors make about their proposed mechanism are “pretty bold”. He adds:
“Each city is so unique…We can find an association, but getting a mechanism has to be [on] a case-by-case basis.”
Van Zandt adds that the redlined maps are a “good proxy”, but not necessarily the driver of inequity. The important part, she says, is “that we identified neighbourhoods that banks should not invest in – and that those patterns persist to today”.
Lived experience
Given the disparities identified in the work, Salazar-Miranda says she hopes that policymakers can incorporate this type of information into funding and other policy decisions. As an added benefit, she says, many of the investments in environmental capital – such as additional green spaces – can improve mental and physical well-being. She adds:
“One of the conversations that would be interesting, from a policy point of view, is how do we bring the types of resources to these communities that can be helpful in mitigating these environmental risks, but also from a social point of view.”
While the findings themselves are not surprising, “it’s great to have systematic assessments” and scientific evidence to back up people’s firsthand knowledge, Shandas says. He tells Carbon Brief:
“Historically disinvested parts of cities tend to be at the frontline of extreme climate events – including flooding and heat. I know the communities that live in the cities that I [have worked with] regularly have brought this up for many, many years.
“The most significant part of this study is that it’s corroborating what the lived experiences of communities have been for quite some time.”
Van Zandt adds:
“It’s not a historical study. It’s a study of what’s happening today and what’s going to continue to happen in the future.”
The post Discriminatory ‘redlining’ increases climate risk in disadvantaged US neighbourhoods appeared first on Carbon Brief.
Discriminatory ‘redlining’ increases climate risk in disadvantaged US neighbourhoods
Colombia wants countries to discuss options for a global agreement to ensure that the extraction, processing and recycling of minerals – including those needed for the clean energy transition – don’t harm the environment and human wellbeing.
The mineral-rich nation is proposing to create an expert group to “identify options for international instruments, including global and legally-binding instruments, for coordinated global action on the environmentally sound management of minerals and metals through [their] full lifecyle”.
Colombia hopes this will eventually lead to an agreement on the need for an international treaty to define mandatory rules and standards that would make mineral value chains more transparent and accountable.
The proposal was set out in a draft resolution submitted to the UN Environment Assembly (UNEA) earlier this week and seen by Climate Home News. UNEA, which is constituted of all UN member states, is the world’s top decision-making body for matters relating to the environment. The assembly’s seventh session will meet in Kenya in December to vote on countries’ proposals.
-
Milei’s budget cuts fuel deforestation fears in Argentina’s Chaco
President Javier Milei has slashed environmental spending since his 2023 election, putting forest defenders on alert in Gran Chaco, South America’s second-largest forest biome -
Why ethics must be at the heart of global climate action
If science shows us the urgency for climate action, then ethics must show us the way to rebuild momentum writes WWF climate & energy lead Manuel Pulgar-Vidal
Soaring demand for the minerals used to manufacture clean energy technologies and electric vehicles, as well as in the digital, construction and defence industries have led to growing environmental destruction, human rights violations and social conflict.
Colombia argues there is an “urgent need” to strengthen global cooperation and governance to reduce the risks to people and the planet.
Options for a global minerals agreement
The proposal is among a flurry of initiatives to strength global mineral governance at a time when booming demand is putting pressure on new mining projects.
Colombia, which produces emeralds, gold, platinum and silver for exports, first proposed the idea for a binding international agreement on minerals traceability and accountability on the sidelines of the UN biodiversity talks it hosted in October 2024.
Since then, the South American nation has been quietly trying to drum up support for the idea, especially among African and European nations.
Its draft resolution to UNEA7 contains very few details, leaving it open for countries to discuss what kind of global instrument would be best suited to make mineral supply chains more transparent and sustainable.
Does the world need a global treaty on energy transition minerals?
Colombia says it wants the expert group to build on other UN initiatives, including a UN Panel on Critical Energy Transition Minerals, which set out seven principles to ensure the mining, processing and recycling of energy transition minerals are done responsibly and benefit everyone.
The group would include technical experts and representatives from international and regional conventions, major country groupings as well as relevant stakeholders.
It would examine the feasibility and effectiveness of different options for a global agreement, consider their costs and identify measures to support countries to implement what is agreed.
The resolution also calls for one or two meetings for member states to discuss the idea before the UNEA8 session planned in late 2027, when countries would decide on a way forward.
No time to lose for treaty negotiations
Colombia’s efforts to advance global talks on mineral supply chains have been welcomed by resource experts and campaigners. But not everyone agrees on the best strategy to move the discussion forward at a time when multilateralism is coming under attack.
Johanna Sydow, a resource policy expert who heads the international environmental policy division of the Heinrich-Böll Foundation, said she had hoped that the resolution would explicitly call for negotiations to begin on an international minerals treaty.
“Treaty negotiations take a long time. If you don’t even start with it now, it will take even longer. I don’t see how in two or three years it will be easier to come to an agreement,” she told Climate Home.
-
The company tracking energy transition minerals back to the mines
Australian firm Source Certain traces minerals back to the exact point where they were extracted from the Earth – a technique that could help make cleantech supply chains more accountable -
The ICJ climate ruling has major implications for the loss and damage fund
As the fund struggles with lack of money and bureaucratic barriers, its board must align its actions with the landmark court decision -
Major financiers neglect energy transition risks from mining as demand booms
Financial institutions are lacking safeguards to prevent harms caused by mining the resources needed for the energy transition, analysis of the sector’s financing finds
Despite the geopolitical challenges, “we need joint rules to prevent a huge race to the bottom for [mineral] standards”. That could start with a group of countries coming together and starting to enforce joint standards for mining, processing and recycling minerals, she said.
But any meaningful global agreement on mineral supply chains would require backing from China, the world’s largest processor of minerals, which dominates most of the supply chains. And with Colombia heading for an election in May, it will need all the support it can get to move its proposal forward.
‘Voluntary initiative won’t cut it’
Juliana Peña Niño, Colombia country manager at the Natural Resource Governance Institute, is more optimistic. “Colombia’s leadership towards fairer mineral value chains is a welcome step,” she told Climate Home News.
“At UNEA7, we need an ambitious debate that gives the proposed expert group a clear mandate to advance concrete next steps — not delay decisions — and that puts the voices of those most affected at the centre. One thing is clear: the path forward must ultimately deliver a binding instrument, as yet another voluntary initiative simply won’t cut it,” she said.
More than 50 civil society groups spanning Latin America, Africa and Europe previously described Colombia’s work on the issue as “a chance to build a new global paradigm rooted in environmental integrity, human rights, Indigenous Peoples’ rights, justice and equity”.
“As the energy transition and digitalisation drive demand for minerals, we cannot afford to repeat old extractive models built on asymmetry – we must redefine them,” they wrote in a statement.
Main image: The UN Environment Assembly is hosted in Nairobi, Kenya. (Natalia Mroz/ UN Environment)
The post Colombia proposes expert group to advance talks on minerals agreement appeared first on Climate Home News.
Colombia proposes expert group to advance talks on minerals agreement
If you’re young, pregnant and Latina, chances are you live near agricultural fields sprayed with higher levels of brain-damaging organophosphate pesticides.
A baby in the womb has few defenses against industrial petrochemicals designed to kill.
California Sanctions Stark Disparities in Pesticide Exposure During Pregnancy
Climate Change
DeBriefed 3 October 2025: UK political gap on climate widens; Fossil-fuelled Typhoon Ragasa; ‘Overshoot’ unknowns
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Shattered climate consensus
FRACKING BAN: UK energy secretary Ed Miliband has announced that the government will bring forward its plans to permanently ban fracking, in a move designed to counter a promise from the hard-right Reform party to restart efforts to introduce the practice, the Guardian said. In the same speech, Miliband said Reform’s plans to scrap clean-energy projects would “betray” young people and future generations, the Press Association reported.
ACT AXE?: Meanwhile, Kemi Badenoch, leader of the Conservatives, pledged to scrap the 2008 Climate Change Act if elected, Bloomberg reported. It noted that the legislation was passed with cross-party support and strengthened by the Conservatives.
‘INSANE’: Badenoch faced a backlash from senior Tory figures, including ex-prime minister Theresa May, who called her pledge a “catastrophic mistake”, said the Financial Times. The newspaper added that the Conservatives were “trailing third in opinion polls”. A wide range of climate scientists also condemned the idea, describing it as “insane”, an “insult” and a “serious regression”.
Around the world
- CLIMATE CRACKDOWN: The US Department of Energy has told employees in the Office of Energy Efficiency and Renewable Energy to avoid using the term “climate change”, according to the Guardian.
- FOREST DELAY: Plans for Brazil’s COP30 flagship initiative, the tropical forests forever fund, are “suffer[ing] delays” as officials remain split on key details, Bloomberg said.
- COP MAY BE ‘SPLIT’: Australia could “split” the hosting of the COP31 climate summit in 2026 under a potential compromise with Turkey, reported the Guardian.
- DIVINE INTERVENTION: Pope Leo XIV has criticised those who minimise the “increasingly evident” impact of global warming in his first major climate speech, BBC News reported.
€44.5 billion
The cost of extreme weather and climate change in the EU in the last four years – two-and-a-half times higher than in the decade to 2019, according to a European Environment Agency report covered by the Financial Times.
Latest climate research
- Fossil-fuelled climate change caused around 36% of Typhoon Ragasa’s direct damage to homes and properties in southern China, according to a rapid impact attribution study | Imperial Grantham Institute – Climate Change and the Environment
- Some 86% of the global population are concerned about climate change, according to a survey of 280,000 people in 142 countries and regions | Climate Policy
- A global shift towards a “planetary health diet” could slash emissions and save tens of thousands of lives each day | EAT-Lancet Commission 2025 report
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
Clean energy has met 100% of Great Britain’s electricity demand for a record 87 hours this year so far, according to new Carbon Brief analysis. This is up from just 2.5 hours in 2021 and 64.5 hours in all of 2024. The longest stretch of time where 100% of electricity demand was met by clean energy stands at 15 hours, from midnight on 25 May 2025 through to 3pm on 26 May, according to the analysis.
Spotlight
‘Overshoot’ unknowns
As the chances of limiting global warming to 1.5C dwindle, there is increasing focus on the prospects for “overshooting” the Paris Agreement target and then bringing temperatures back down by removing CO2 from the atmosphere.
At the first-ever Overshoot Conference in Laxenburg, Austria, Carbon Brief asks experts about the key unknowns around warming “overshoot”.
Sir Prof Jim Skea
Chair of the Intergovernmental Panel on Climate Change (IPCC) and emeritus professor at Imperial College London’s Centre for Environmental Policy
So there are huge knowledge gaps around overshoot and carbon dioxide removal (CDR). As it’s very clear from the themes of this conference, we don’t altogether understand how the Earth would react in taking CO2 out of the atmosphere.
We don’t understand the nature of the irreversibilities and we don’t understand the effectiveness of CDR techniques, which might themselves be influenced by the level of global warming, plus all the equity and sustainability issues surrounding using CDR techniques.
Prof Kristie Ebi
Professor at the University of Washington’s Center for Health and the Global Environment
There are all kinds of questions about adaptation and how to approach effective adaptation. At the moment, adaptation is primarily assuming a continual increase in global mean surface temperature. If there is going to be a peak – and of course, we don’t know what that peak is – then how do you start planning? Do you change your planning?
There are places, for instance when thinking about hard infrastructure, [where overshoot] may result in a change in your plan – because as you come down the backside, maybe the need would be less. For example, when building a bridge taller. And when implementing early warning systems, how do you take into account that there will be a peak and ultimately a decline? There is almost no work in that. I would say that’s one of the critical unknowns.
Dr James Fletcher
Former minister for public service, sustainable development, energy, science and technology for Saint Lucia and negotiator at COP21 in Paris.
The key unknown is where we’re going to land. At what point will we peak [temperatures] before we start going down and how long will we stay in that overshoot period? That is a scary thing. Yes, there will be overshoot, but at what point will that overshoot peak? Are we peaking at 1.6C, 1.7C, 2.1C?
All of these are scary scenarios for small island developing states – anything above 1.5C is scary. Every fraction of a degree matters to us. Where we peak is very important and how long we stay in this overshoot period is equally important. That’s when you start getting into very serious, irreversible impacts and tipping points.
Prof Oliver Geden
Senior fellow and head of the climate policy and politics research cluster at the German Institute for International and Security Affairs and vice-chair of IPCC Working Group III
[A key unknown] is whether countries are really willing to commit to net-negative trajectories. We are assuming, in science, global pathways going net-negative, with hardly any country saying they want to go there. So maybe it is just an academic thought experiment. So we don’t know yet if [overshoot] is even relevant. It is relevant in the sense that if we do, [the] 1.5C [target] stays on the table. But I think the next phase needs to be that countries – or the UNFCCC as a whole – needs to decide what they want to do.
Prof Lavanya Rajamani
Professor of international environmental law at the University of Oxford
I think there are several scientific unknowns, but I would like to focus on the governance unknowns with respect to overshoot. To me, a key governance unknown is the extent to which our current legal and regulatory architecture – across levels of governance, so domestic, regional and international – will actually be responsive to the needs of an overshoot world and the consequences of actually not having regulatory and governance architectures in place to address overshoot.
Watch, read, listen
FUTURE GAZING: The Financial Times examined a “future where China wins the green race”.
‘JUNK CREDITS’: Climate Home News reported on a “forest carbon megaproject” in Zimbabwe that has allegedly “generated millions of junk credits”.
‘SINK OR SWIM’: An extract from a new book on how the world needs to adapt to climate change, by Dr Susannah Fisher, featured in Backchannel.
Coming up
- 7 October: International Energy Agency (IEA) renewables 2025 report launch
- 8-10 October: World summit of Indigenous peoples and nature, Abu Dhabi, UAE
- 9-15 October: International Union for the Conservation of Nature (IUCN) 2025 congress, Abu Dhabi, UAE
Pick of the jobs
- UK government foreign, commonwealth and development office, senior climate policy adviser | Salary: CA$93,207. Location: Calgary, Canada
- Wellcome Trust, senior research manager, climate and health | Salary: £64,800. Location: London
- Bloomberg, product manager – climate, nature and sustainability regulations | Salary: Unknown. Location: London
DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.
This is an online version of Carbon Brief’s weekly DeBriefed email newsletter. Subscribe for free here.
The post DeBriefed 3 October 2025: UK political gap on climate widens; Fossil-fuelled Typhoon Ragasa; ‘Overshoot’ unknowns appeared first on Carbon Brief.
Doing What’s “Right” Is More Controversial than it Seems
Trump’s Agenda Is Even Far-Reaching Than People May Think
We’re this close to a huge climate win
Spanish-language misinformation on renewable energy spreads online, report shows
The toxic gas flares fuelling Nigeria’s climate change – BBC News
Guest post: Why China is still building new coal – and when it might stop
-
Climate Change2 years ago
Spanish-language misinformation on renewable energy spreads online, report shows
-
Climate Change Videos2 years ago
The toxic gas flares fuelling Nigeria’s climate change – BBC News
-
Climate Change2 months ago
Guest post: Why China is still building new coal – and when it might stop
-
Greenhouse Gases1 year ago嘉宾来稿：满足中国增长的用电需求 光伏加储能“比新建煤电更实惠”
-
Climate Change1 year ago嘉宾来稿：满足中国增长的用电需求 光伏加储能“比新建煤电更实惠”
-
Greenhouse Gases2 months ago
Guest post: Why China is still building new coal – and when it might stop
-
Carbon Footprint1 year agoUS SEC’s Climate Disclosure Rules Spur Renewed Interest in Carbon Credits
-
Renewable Energy3 months ago
US Grid Strain, Possible Allete Sale