Ever since some of the earliest projections of climate change were made back in the 1970s, they have been remarkably accurate at predicting the rate at which global temperatures would rise. For decades, climate change has proceeded at roughly the expected pace, says David Armstrong McKay, a climate scientist at the University of Exeter, in England. Its impacts, however, are accelerating—sometimes far faster than expected.

For a while, the consequences weren’t easily seen. They certainly are today. The Southwest is sweltering under a heat dome. Vermont saw a deluge of rain, its second 100-year storm in roughly than a decade. Early July brought the hottest day globally since records began—a milestone surpassed again the following day. “For a long time, we were within the range of normal. And now we’re really not,” Allegra LeGrande, a physical-research scientist at Columbia University, told me. “And it has happened fast enough that people have a memory of it happening.”

In fact, a growing number of climate scientists now believe we may be careening toward so-called tipping points, where incremental steps along the same trajectory could push Earth’s systems into abrupt or irreversible change—leading to transformations that cannot be stopped even if emissions were suddenly halted. “The Earth may have left a ‘safe’ climate state beyond 1°C global warming,” Armstrong McKay and his co-authors concluded in Science last fall. If these thresholds are passed, some of global warming’s effects—like the thaw of permafrost or the loss of the world’s coral reefs—are likely to happen more quickly than expected. On the whole, however, the implications of blowing past these tipping points remain among climate change’s most consequential unknowns: We don’t really know when or how fast things will fall apart.

Some natural systems, if upended, could herald a restructuring of the world. Take the Thwaites Glacier in West Antarctica: It’s about the size of Florida, with a protruding ice shelf that impedes the glacier’s flow into the ocean. Although the ice shelf's overall melt is slower than originally predicted, warm water is now eating away at it from below, causing deep cracks. At a certain point, that melt may progress enough to become self-sustaining, which would guarantee the glacier’s eventual collapse. How that plays out will help determine how much sea levels will rise—and thus the future of millions of people.

The fate of the Thwaites Glacier could be independent of other tipping points, such as those affecting mountain-glacier loss in South America, or the West African monsoon. But some tipping points will interact, worsening one another’s effects. When melt from Greenland’s glaciers enters the ocean, for example, it alters an important system of currents called the Atlantic Meridional Overturning Circulation. The AMOC is like a conveyor belt, drawing warm water from the tropics north. The water’s salinity increases as it evaporates, which, among other factors, makes it sink and return south along the ocean floor. As more glacial fresh water enters the system, that conveyor belt will weaken. Right now it’s the feeblest it’s been in more than 1,000 years.

[Read: I’ve hit my climate tipping point]

A shutdown of that ocean current could dramatically alter phenomena as varied as global weather patterns and crop yields. Messing with complex systems is chilling precisely because there are so many levers: If the temperature of the sea surface changes, precipitation over the Amazon might too, contributing to its deforestation, which in turn has been linked to snowfall on the Tibetan plateau. We may not even realize when we start passing points of no return—or if we already have. “It’s kind of like stepping into a minefield,” Armstrong McKay said. “We don’t want to find out where these things are by triggering them.”

One grim paper that came out last year, titled “Climate End Game,” mapped out some of the potential catastrophes that could follow a “tipping cascade,” and considered the possibility that “a sudden shift in climate could trigger systems failures that unravel societies across the globe.” Chris Field, the director of the Stanford Woods Institute for the Environment and a contributor to several IPCC reports, warned that “at some point, the impacts of the climate crisis may become so severe that we lose the ability to work together to deliver solutions.”

James Hansen, one of the early voices on climate, says that measures to mitigate the crisis may now, ironically, be contributing to it. He published a working paper this spring suggesting that a reduction in sulfate aerosol particles—or the air pollution associated with burning coal and the global shipping industry—has contributed to warmer temperatures. That’s because these particles cause water droplets to multiply, which brightens clouds and reflects solar heat away from the planet’s surface. Though the paper has not been peer-reviewed, Hansen predicts that environmentally minded policies to reduce these pollutants will likely cause temperatures to rise by 2 degrees Celsius by 2050.

[Read: ‘Things don’t always change in a nice, gradual way’]

Even before the climate gets to that point, we may face a dramatic uptick in climate-related disasters, says William Ripple, a distinguished professor of ecology at Oregon State University and the lead author of a recent commentary on the “risky feedback loops” connecting climate-driven systems. There’s a sense of awe—in the original meaning of inspiring terror or dread—at witnessing such sweeping changes play out across the landscape. “Many scientists knew these things would happen, but we’re taken aback by the severity of the major changes we’re seeing,” Ripple said. Armstrong McKay likened the challenge of being a climate scientist in 2023 to that faced by medical professionals: “You put a certain emotional distance between you and the work in order to do the work effectively,” he said, “that can be difficult to maintain.”

Although it may be too late to avert some changes, others could still be staved off by limiting emissions. LeGrande said she worries that talking about tipping points may encourage people to think that any further action now is futile. In fact, the opposite is true, Ripple said. “Scientifically, everything we do to avoid even a tenth of a degree of temperature increase makes a huge difference.”

Welcome to Up for Debate. Each week, Conor Friedersdorf rounds up timely conversations and solicits reader responses to one thought-provoking question. Later, he publishes some thoughtful replies. Sign up for the newsletter here.

This is the second batch of reader responses to the Supreme Court’s affirmative-action decision. Batch one is here.

Replies have been edited for length and clarity.

Matt argues that the stakes are lower than many think:

I find the competition for all the elite schools really out of touch with the reality of most people. As a high schooler, I bombed the SAT. I hadn’t figured anything out in my life, so I decided to do two years at a community college, then transfer to a larger state school in rural Appalachia. I did well and graduated with honors. Everyone should get a fair shake at life. But when you have to divvy up a limited number of spots, there’s going to be some winners and losers. It’s just that some of the “losers” in the competition for admissions to Harvard are going to end up attending their secondary-choice Ivy on full rides.

Lucretia laments the decision:

It seems to me that affirmative action is an attempt to make up for the failure to provide basic services in schools, health care, policing, and other services in poor, Black, and First Nation communities. I would suggest that poverty and systemic racism are the problem and need to be corrected. Until they are, affirmative action is probably necessary.

Mary urges colleges to work around the decision:

As long as racism and other prejudices persist, affirmative action will be necessary. As long as we continue to have opportunity gaps by race, class, language, religion, and gender, we will need strategies in place to eliminate those gaps. For the selective colleges and universities that will be most impacted, we need to rethink recruitment and we need to be more intentional about partnerships with high schools and community colleges.

If we are serious about racial diversity on our campuses, we need to partner with organizations and leaders in communities of color to actively recruit future students, and we need to start before the senior year of high school. College-going identity starts to solidify in middle school so we need to start there. We can’t wait for students to come to us. We need to tap into our alumni of color and current students of color to partner in these recruitment efforts. We also need a multipronged strategy to rethink admissions. We can do that by reducing or eliminating legacy admissions. Due to a long-standing history of racism in the U.S., our city neighborhoods and suburban communities are already racially segregated. We can also take geography into consideration by zip code, census tract, and even census block. We can ramp up holistic admissions and give more weight to essays, interviews, and other qualitative measures.

Anna questions a premise of using race in college admissions:

Ending race-based admissions is a good decision because “race” is not a category in which we can segregate people. The national census has trouble even correctly counting representatives of each race. The concept of race as in skin color (Black, white etc.) is racist and colonialist in nature. Many Black people in South America have been living there for generations, becoming part of those nations, integrating into society, becoming Latino. Who are we to assign them to other [races]? And what about mixed children? How should we consider them—if you’re Black and white, does it cancel each other out? Should children looking more Black be officially considered more disadvantaged than their lighter-toned counterparts with the same parentage?

If one of your grandparents was black and it really shows, should you be treated differently than someone whiter, but with three Black grandparents and rare genetics that made that happen? If you are Black Indigenous, are you different from white Indigenous? When you look at income, which is going to benefit minorities disproportionately anyway, you can much more easily divide people into nonarbitrary categories.

Mark defends the use of race in admissions:

The concepts of fairness and justice do not arise in a vacuum, detached from the human societies that create them. Once upon a time, society considered trial by combat “fair.” The notion that we should not take race into account when considering admissions would be more palatable if we truly lived in a color-blind society (which I am an advocate for). We do not. Ours is a society in which race still privileges and disadvantages certain peoples. As long as that is the case, affirmative action is necessary.

Indeed, ideologies like critical race theory arise because minorities are not given a seat at the table and reject the systems of society, even if they happen to be good systems. If we want to preserve the good parts of society (and there are good parts of Western civilization), we need to have minority groups participate and benefit from that system—otherwise they are justified in tearing it down. Affirmative action is not just a moral good, it serves a profoundly practical purpose—to keep society stable and strengthen trust in our institutions.

H. is a gay white male from the South who now attends a top-20 private institution.

I do not believe in affirmative action. The issue with admissions isn’t race, it’s wealth. Many of the people of color at my predominantly white college come from vastly wealthy backgrounds and attended premier boarding schools across the world (Eton, St. Andrews, Exeter, etc.). It is oversimplifying the issue of representation to boil this debate down to race. Although it is true people of color are more likely to be impoverished, have fewer resources, and attend worse public schools, white and Asian people in underfunded communities experience this, too. I went to a public school that was severely underfunded, and my family could afford no tutors or enrichment programs. My high school was majority white. We all experienced an equal lack of resources. What is the value of biasing applicants by race, if the similarity with their white peers is yachting or using summer as a verb? While admissions should strive to reflect the demographic makeup of this nation, they should reflect the financial background of it as well.

Hilary, “a lifelong liberal,” writes:

As an Asian American I agree with the Supreme Court’s striking down the use of race in college admissions. I find it patently unfair that the average Asian American admitted to Harvard has SAT scores higher than African Americans who are admitted, and also higher than whites. Why should my teen be so disadvantaged for college admissions based on his race? Many of the current African American, Hispanic, and Native American admits aren’t from economically disadvantaged backgrounds. I believe that universities should scrap preferences for athletes, children of faculty, donors, and legacies, and pursue socioeconomic and political diversity instead of racial diversity. Race and ethnicity shouldn’t be factors.

Matthew defends the principle of race neutrality in law:

Even as a solid liberal, I have always been flummoxed by the left’s insistence that using race in higher admissions is acceptable. It is a classic example of “ends justify the means” thinking and it undermines foundational principles we should all agree on. Justice Jackson was correct to say that “deeming race irrelevant in law does not make it so in life.” But race’s relevance in life does not mean it should be relevant in the law.

One of the law’s purposes is to lay out neutral principles that can be fairly applied across the board. If we agree as a society that people should not be treated differently because of their race (and I hope we do), then there is no principled way to say using race in admissions upholds this ideal. Further, as a legal matter, if we say that diversity in college is a “compelling government interest” that meets the constitutional requirements of strict scrutiny, then practically anything is fair game for the use of race.

There are many principles that provide bedrock support for a well-functioning and just society even if they are not true in any factual sense. For example, we presume those charged with a crime are innocent until proven guilty beyond a reasonable doubt using admissible evidence. This procedural protection makes our society a better place to live overall, and it is more fundamental than any one case.

Suppose a person commits a murder but walks free because the available admissible evidence could not prove guilt beyond a reasonable doubt (e.g., all witnesses have died of natural causes). We consider this an acceptable outcome because it was the correct result of a system whose principles we support. If we give in to the temptation to make an exception in this one case, then we beg the question of why we even had the system in the first place. And where do we draw the line? And who decides where to draw it?

In the same way, we have a principle that people should not be treated differently before the law based on their race. The fact that Black Americans in particular are subjected to racism and discrimination, including by the government, does not justify using race as a general mechanism to balance the scales. Who exactly is deciding how to do the balancing?

This is by no means to suggest the law is powerless to right past wrongs. If an employer discriminates against Black employees, they can be sued. This means the actual perpetrator is held responsible for their actions. We don’t punish all employers in the industry as a group. Even in the case of more systemic wrongs, there is a way to be more rigorous in our response. We paid reparations to Japanese Americans who were interned during World War II, and we could pay reparations for slavery without putting the burden on any one group based on their immutable characteristics.

In the case of affirmative action, however, we apparently decided that Asian and white college applicants should bear the burden of the sins of their parents’ generation. After all, college admissions at a competitive school is by definition zero-sum. It is odd to me that the left has fought so hard to defend the use of race in such a specific context. After all, most colleges accept the majority of applicants. Affirmative action only really affects a select few of the world’s most competitive schools. This strikes me as a Band-Aid on a serious wound. The interventions needed to minimize or reverse the effects of systemic racism must happen much earlier. Undoing redlining or properly funding poorer school districts would go much farther to making our society more equal. These interventions can also be justified without treating individuals only as members of racial groups.

Affirmative action was always destined to be a Pyrrhic victory at best.

Daniel has a suggestion:

If one wanted to return to the original idea for affirmative action, perhaps the answer is to award points to college applicants—regardless of race—who are descended from people enslaved in the United States.

S.B. believes there is a strong case for focusing on economic disadvantage:

I’m a white student from a low-income background at a very selective private school in Massachusetts. My college has been writing emails to the student body about how important affirmative action is to their admissions process and how this decision harms their ability to “attract and educate a community made up of many different kinds of students.” I hope, though, that this decision will create a better education system for students of all races, and that it will motivate schools to focus more on factors like class and geography when making admissions decisions. The best way to fix the racial wealth gap is to better support all economically disadvantaged people. There is no way in which helping poor people of one race hurts poor people of another race; therefore there is no good rationale for affirmative action as a way to solve economic inequality.

Then the primary motivation for race-conscious admissions is social diversity, something I do feel I have benefitted from as a student. However, I believe colleges should look deeper than race and create communities of people who don’t just look different but think and act differently.

James argues that “as a civilization, we have to move beyond skin color as an essential quality of a person before it’s the undoing of our societies, because of one inescapable point nearly everyone misses: The mind fundamentally finds security in homogeneity—the known, familiar and safe—and there is literally nothing we can do about it except stop separating people into the other.”

Since late 2021, Europe has been gripped by its worst-ever outbreak of bird flu, while North and South America have also experienced severe outbreaks.