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Claim: Maximum US temperatures for the last 12 months were cooler than for the same period for 2011-2012, despite 700 billion tons of emissions. If every emission warms the planet, how can that be?
Fact: Misleading. The claim misunderstands how climate science works. Short-term temperature fluctuations, such as cooler periods, can occur due to natural factors like El Niño and La Niña cycles, which influence weather patterns yearly. However, the long-term trend remains clear: U.S. temperatures have risen consistently by about 0.5°F per decade since the 1970s. Global warming is a cumulative process, and short-term variations don’t contradict the overall warming caused by greenhouse gas emissions.
Claim Post:
https://x.com/JunkScience/status/1849623777019097147
What does the post say
A Twitter user recently claimed that U.S. temperatures over the past 12 months were cooler than in 2011-2012 despite an increase of 700 billion tons of emissions. The post suggests that if carbon emissions directly raise global temperatures, a cooler year in the U.S. should not occur, casting doubt on human-caused climate change. The user argues that this observed cooling challenges the idea that emissions consistently contribute to global warming, implying flaws in the mainstream understanding of climate science. This claim assumes that all emissions should immediately impact temperature without accounting for natural climate variability or the lagged, cumulative nature of greenhouse gas effects on global climate. By focusing on short-term fluctuations, the claim overlooks decades of scientific data showing a steady rise in global temperatures despite temporary, localised cooling trends.
What we found
This claim is misleading. While recent temperatures in the U.S. may appear cooler compared to specific previous years, this short-term regional variation does not invalidate the overall global warming trend. Climate change is a long-term phenomenon driven by the gradual accumulation of greenhouse gases in the atmosphere, and short-term fluctuations in a single region are expected and documented. The broader scientific consensus remains clear: global temperatures rise due to human activities, and isolated data points do not contradict this reality.
Short-Term Weather vs. Long-Term Climate Trends
One of the primary misunderstandings in the claim is the conflation of short-term weather patterns with long-term climate trends. Weather refers to local atmospheric conditions over days, months, or years, while climate represents global average conditions over much more extended periods (decades to centuries). Short-term cooling in a specific region, such as the contiguous U.S., does not contradict long-term global warming; instead, it reflects natural variability within the climate system.
Multiple factors, such as oceanic cycles and atmospheric conditions, can influence short-term temperature fluctuations. For example, El Niño and La Niña events are significant climate phenomena that periodically warm and cool global temperatures. The 2011-2012 period was influenced by a La Niña event, which often leads to cooler conditions in parts of North America, while more recent years have seen both La Niña and El Niño phases influencing weather patterns. These fluctuations are normal and well-documented by climate scientists.
This natural variability within specific regions is expected and does not alter the overall trend of global warming driven by the accumulation of greenhouse gases. Scientists analyse climate change by examining decadal or multi-decadal trends rather than yearly or localised data points, as short-term variations are considered “noise” within the broader signal of long-term warming.
The Impact of Greenhouse Gas Emissions on Global Climate
Global warming is driven mainly by the cumulative buildup of greenhouse gases in the atmosphere, particularly carbon dioxide (CO₂). Emitted through fossil fuel combustion, industrial activities, and deforestation, CO₂ remains in the atmosphere for centuries, contributing to a “greenhouse effect” that traps heat and leads to gradual warming of the Earth. The scientific consensus, affirmed by bodies like the Intergovernmental Panel on Climate Change (IPCC), holds that the continuous increase in greenhouse gas concentrations is the primary driver of global long-term warming trends.
It is important to note that the effect of each additional ton of CO₂ does not lead to an immediate temperature spike; instead, the warming occurs gradually over decades as gases accumulate and persist in the atmosphere. This gradual, long-term impact is why scientists focus on global, multi-year averages rather than annual variations when assessing climate change.
According to the IPCC Sixth Assessment Report, human-induced warming has caused global temperatures to rise by over 1°C since the late 19th century, with most of this warming occurring over the last few decades. The long-term data is precise: global average temperatures are rising, with the previous decade being the warmest worldwide, despite occasional cooling periods in specific regions or years. This steady increase aligns with greenhouse gas concentration trends, underscoring the cumulative impact of emissions on the Earth’s climate system.
Regional Cooling Does Not Negate Global Warming
The claim highlights cooler U.S. temperatures over a year and questions the warming trend. However, focusing on short-term data in a single region misrepresents the nature of climate change, which is global in scope. The United States represents less than 2% of the Earth’s surface area, and even significant regional cooling in the U.S. would not be enough to offset global averages.
NOAA and NASA data show that global temperatures have consistently risen even with cooler-than-average temperatures in some years for the U.S.. For example, 2023 has been among the hottest years globally, despite variations within the U.S. This increase in global temperature records, rather than single-year cooling events, reflects the real impact of greenhouse gases on climate. Isolated regional data, as used in the claim, needs to account for global averages, which is why scientific assessments rely on worldwide data.
Another critical point is that short-term cooling events often result from temporary phenomena. In recent years, the La Niña climate pattern has brought cooler temperatures to specific parts of the world, including the U.S., while contributing to a global long-term warming trend. Events like these underscore that natural climate cycles can cause temporary cooling or warming but do not interfere with the overarching pattern of human-driven climate change.
Scientific Consensus on Global Warming
The overwhelming consensus among climate scientists is that human activities, particularly the release of greenhouse gases, are the primary drivers of global warming. Research by leading institutions, including the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), and the IPCC, confirms that rising greenhouse gas levels correlate closely with long-term increases in global temperatures. These findings are based on decades of research and multiple lines of evidence, including satellite data, historical temperature records, and climate modelling.
The IPCC’s 2021 report states with high confidence that each of the last four decades has been successively warmer than any decade that preceded it since 1850. The report also emphasises that continued emissions of greenhouse gases will lead to further warming and more frequent extreme weather events. Thus, while regional temperatures may fluctuate due to short-term factors, the underlying warming trend remains clear.
The Fifth National Climate Assessment, a U.S. government report led by NOAA, also highlights significant warming trends across the U.S., with impacts on ecosystems, agriculture, and public health. This comprehensive scientific assessment affirms that climate change affects every region of the United States and that these impacts are expected to intensify over time.
The claim that cooler U.S. temperatures over the past 12 months invalidate climate change is misleading and based on a misunderstanding of climate science. While short-term, localised cooling is possible due to natural variability, these fluctuations do not undermine the well-documented global warming trend driven by human activity. Climate science distinguishes between short-term weather events and long-term climate patterns, and focusing on one year’s data in one region ignores the broader global picture. The scientific consensus remains firm: greenhouse gas emissions have led to a significant and ongoing increase in global temperatures. While regional and short-term cooling can occur, these do not alter the reality of a warming planet.
References:
https://www.epa.gov/climate-indicators/climate-change-indicators-us-and-global-temperature
https://www.ipcc.ch/2021/08/09/ar6-wg1-20210809-pr
https://science2017.globalchange.gov/chapter/6
https://www.weather.gov/iwx/la_nina
https://climate.nasa.gov/causes
https://nca2023.globalchange.gov
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