Net-Zero Emissions: U.S. and Iran, the Only Major Emitters Without Formal Targets

Only two major players in the global economy, the United States and Iran, have not yet formalized net-zero emission targets. This striking conclusion comes from a recent fact-checking effort by Carbon Brief, a leading reference site for climate science and policy. While the international community increasingly aligns with commitments to drastically reduce greenhouse gas emissions, this uniqueness of the two countries raises major questions about global climate ambition and the reliability of future projections.

The Global Race for Net-Zero: Where Are We?

The net-zero objective, or "net-zero," has become the cornerstone of the global strategy to limit global warming to +1.5°C above pre-industrial levels, in line with the Paris Agreement. It involves balancing greenhouse gas emissions with their removal from the atmosphere, either through natural sinks (forests) or technological capture. According to Carbon Brief's analysis, nearly all major economies and top global emitters have now enshrined this objective in their legislation or political declarations.

China, the European Union, India, Japan, the United Kingdom, Canada, Australia, Brazil, South Africa, and many others have all announced carbon neutrality targets, generally by 2050 or 2060 for China and India. These commitments, while varying in scope and timeline, send a strong signal about the direction of international climate policy. They serve as the basis for predictive models to assess future emission trajectories and climate warming scenarios.

Why Are These Objectives Crucial for the Climate?

Net-zero objectives are not mere political statements; they are scientifically substantiated. The reports of the Intergovernmental Panel on Climate Change (IPCC) have clearly demonstrated that achieving net-zero by mid-century is essential to avoid the most catastrophic consequences of climate change. Without drastic and rapid reductions in emissions, atmospheric greenhouse gas concentrations will continue to rise, leading to global temperature increases and intensification of extreme weather events.

These objectives guide investments in renewable energy, energy efficiency, transport electrification, and technological innovation. They create a framework for public policy and incentivize the private sector to adapt. For scientists and organizations like the ECMWF (European Centre for Medium-Range Weather Forecasts) or Copernicus, the lack of clear commitments from certain major actors introduces significant forecast uncertainty in their long-term climate models. Understanding the intentions of the largest emitters is fundamental to refining future scenarios.

The U.S. and Iran: Climate Trajectories Under the Scrutiny of Models

The United States, the second-largest historical emitter and current emitter, does not have federal legislation or an executive order setting a net-zero target. While the Biden administration has reaffirmed its ambition to reduce emissions by 50-52% by 2030 compared to 2005 and achieve net-zero by 2050, these objectives are not legally binding at the national level, making them vulnerable to future policy changes. This situation starkly contrasts with, for example, the United Kingdom, where the 2050 net-zero target has been enshrined in law since 2019.

Iran, for its part, is a major player in hydrocarbon production and has not set a net-zero target either. Its climate policy is complex, often influenced by geopolitical and economic considerations. The absence of these two nations from the group of countries with formal targets stands out because they represent significant emission sources that directly impact global atmospheric composition.

The predictive models, whether based on physical principles or using machine learning through neural networks like GraphCast or Pangu-Weather for short-term weather forecasting, or climate models for longer-term projections, incorporate emission scenarios. When major countries lack firm commitments, climatologists must work with broader assumptions, increasing the range of forecast uncertainties regarding future warming scenarios and their regional impacts.

The Impact of Inaction on Long-Term Projections

The absence of formal net-zero targets from the U.S. and Iran not only undermines global reduction efforts but also complicates the task of climate scientists. Predictive models are sophisticated tools that process vast amounts of satellite and ground data to simulate the behavior of the climate system. To forecast future evolution, they need clear and credible emission scenarios that reflect the policies and commitments of nations.

Without these firm commitments, neural networks and other machine learning techniques applied to atmospheric data may face greater challenges in refining projections. Uncertainty regarding the future policies of these countries can lead to wider ranges of results in climate projections, making adaptation and mitigation planning more difficult. This means that policymakers and populations may be less prepared for potential impacts, whether they involve heatwaves, prolonged droughts, or intense rainfall events, whose frequency and intensity are analyzed by systems like those of Copernicus.

International collaboration efforts, essential for addressing the climate crisis, are also put to the test. Other nations that have made commitments may perceive a lack of fairness, which could weaken collective will. Integrated models evaluating global climate policies must then incorporate this divergence, complicating the analysis of optimal paths toward a more sustainable future.

What This Means for Meteorologists and Climatologists

For the scientific community, this situation underscores the importance of continuing to develop ever more robust predictive models, capable of handling significant forecast uncertainty linked to socio-economic and political factors. Progress in machine learning and neural networks, applied to the analysis of atmospheric data and emission scenarios, is more necessary than ever to provide reliable information to decision-makers, even in the face of heterogeneous national climate policies.

Platforms like ECMWF or Copernicus will continue to play a central role in global emissions monitoring and impact evaluation. Their analyses, enriched by the latest advances in AI, will be crucial for understanding the consequences of these divergences and illuminating the path toward more unified climate action. The stake is not just predicting tomorrow's weather but modeling the planet's climate for decades to come, a task complicated by the lack of full consensus on climate objectives.