Human activities are yielding rising atmospheric concentrations of greenhouse gases and other gases and particulates and are also greatly altering the Earth's land cover. A scientific consensus has emerged that those activities, if allowed to continue unabated, will have extensive, highly uncertain, but potentially serious and costly impacts on regional climates and ocean conditions throughout the world. This Congressional Budget Office (CBO) paper-prepared at the request of the Chairman of the Senate Committee on Energy and Natural Resources-presents an overview of the current understanding...

The cost of providing that care has increased rapidly as a share of the defense budget over the past decade, outpacing growth in the economy, growth in per capita health care spending in the United States, and growth in funding for DoD's base budget (which finances the department's routine activities but has excluded funding for operations in Iraq and Afghanistan). Between 2000 and 2012, funding for military health care increased by 130 percent, over and above the effects of overall inflation in the economy. In 2000, funding for health care accounted for about 6 percent of DoD's base budget;...

The Congress faces an array of policy choices as it confronts the dramatic increase in the federal government's debt over the past several years and the prospect of large annual budget deficits and further increases in that debt that are projected to occur in coming decades under current law (see Figure 1-1). To help inform lawmakers about the budgetary implications of various approaches to changing federal policies, the Congressional Budget Office (CBO) periodically issues a compendium of policy options that would affect the federal budget as well as separate reports that include policy...

In most years, the Department of Defense (DoD) provides a five-year plan, called the Future Years Defense Program (FYDP), associated with the budget that it submits to the Congress. Because decisions made in the near term can have consequences for the defense budget well beyond that period, the Congressional Budget Office (CBO) regularly examines DoD's FYDP and projects its budgetary impact roughly a decade beyond the period covered by the FYDP. For this analysis, CBO used the FYDP that was provided to the Congress in April 2013; that FYDP spans fiscal years 2014 to 2018, and CBO's...

Roughly half of the Army's combat forces at the end of 2005 were so-called heavy units-forces that are equipped with armored vehicles and that provide significant firepower. To support those units, the Army maintains a fleet of approximately 28,000 armored vehicles. Now that the Cold War is over, some defense experts have questioned the relevance of such vehicles to the current national security strategy and their continued usefulness (notwithstanding their contributions to recent operations, such as Desert Storm and Iraqi Freedom). The average age of the armored combat vehicle fleet at the...

The United States maintains a considerable capability to attack ground targets with conventional weapons anywhere in the world. Air Force, Navy, and Marine Corps tactical aircraft deployed to forward locations can be used for ground attack, or "strike" missions, in the region where their bases or aircraft carriers are located, and a similar regional capability is offered by Tomahawk cruise missiles launched from submarines or surface ships. If air bases or aircraft carriers are not available in the region, long-range strike capability can be provided by the Air Force's smaller fleet of...

The federal budget deficit has fallen sharply during the past few years, and it is on a path to decline further this year and next year. The Congressional Budget Office (CBO) estimates that under current law, the deficit will total $514 billion in fiscal year 2014, compared with $1.4 trillion in 2009. At that level, this year's deficit would equal 3.0 percent of the nation's economic output, or gross domestic product (GDP)-close to the average percentage of GDP seen during the past 40 years. As it does regularly, CBO has prepared baseline projections of what federal spending, revenues, and...

Lawmakers could increase federal revenues and encourage reductions in emissions of carbon dioxide (CO2) by establishing a carbon tax, which would either tax those emissions directly or tax fuels that release CO2 when they are burned (fossil fuels, such as coal, oil, and natural gas). Emissions of CO2 and other greenhouse gases accumulate in the atmosphere and contribute to climate change-a long-term and potentially very costly global problem. The effects of a carbon tax on the U.S. economy would depend on how the revenues from the tax were used. Options include using the revenues to reduce...

One of lawmakers' highest health-related priorities is adding a prescription drug benefit to Medicare. Although that program gives older Americans broad insurance coverage for many health needs, it provides only limited coverage of drugs not dispensed during a hospital stay. That gap in coverage has become increasingly significant as prescription drugs have assumed greater importance in the treatment of disease and as spending for outpatient prescription drugs has soared. Designing a Medicare drug benefit is a complex task, however. The competing goals for such a benefit mean that...

President Obama has announced that all U.S. combat operations for the war in Iraq-also called Operation Iraqi Freedom (OIF)-will cease by the end of August 2010. According to the timeline described by Administration officials, the approximately 128,000 U.S. military personnel currently in Iraq would remain there through the Iraqi elections scheduled for January 2010. After that, U.S. forces would decline to no more than 50,000 troops by the end of August 2010. In accordance with the Status of the Forces Agreement signed by Iraq and the United States in November 2008, the remaining 50,000 U.S....